Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

5 files changed, 2757 insertions, 0 deletions

diff --git a/Documentation/security/keys/core.rst b/Documentation/security/keys/core.rst
new file mode 100644
index 000000000..326b8a973
--- /dev/null
+++ b/Documentation/security/keys/core.rst
@@ -0,0 +1,1849 @@
+============================
+Kernel Key Retention Service
+============================
+
+This service allows cryptographic keys, authentication tokens, cross-domain
+user mappings, and similar to be cached in the kernel for the use of
+filesystems and other kernel services.
+
+Keyrings are permitted; these are a special type of key that can hold links to
+other keys. Processes each have three standard keyring subscriptions that a
+kernel service can search for relevant keys.
+
+The key service can be configured on by enabling:
+
+	"Security options"/"Enable access key retention support" (CONFIG_KEYS)
+
+This document has the following sections:
+
+.. contents:: :local:
+
+
+Key Overview
+============
+
+In this context, keys represent units of cryptographic data, authentication
+tokens, keyrings, etc.. These are represented in the kernel by struct key.
+
+Each key has a number of attributes:
+
+	- A serial number.
+	- A type.
+	- A description (for matching a key in a search).
+	- Access control information.
+	- An expiry time.
+	- A payload.
+	- State.
+
+
+  *  Each key is issued a serial number of type key_serial_t that is unique for
+     the lifetime of that key. All serial numbers are positive non-zero 32-bit
+     integers.
+
+     Userspace programs can use a key's serial numbers as a way to gain access
+     to it, subject to permission checking.
+
+  *  Each key is of a defined "type". Types must be registered inside the
+     kernel by a kernel service (such as a filesystem) before keys of that type
+     can be added or used. Userspace programs cannot define new types directly.
+
+     Key types are represented in the kernel by struct key_type. This defines a
+     number of operations that can be performed on a key of that type.
+
+     Should a type be removed from the system, all the keys of that type will
+     be invalidated.
+
+  *  Each key has a description. This should be a printable string. The key
+     type provides an operation to perform a match between the description on a
+     key and a criterion string.
+
+  *  Each key has an owner user ID, a group ID and a permissions mask. These
+     are used to control what a process may do to a key from userspace, and
+     whether a kernel service will be able to find the key.
+
+  *  Each key can be set to expire at a specific time by the key type's
+     instantiation function. Keys can also be immortal.
+
+  *  Each key can have a payload. This is a quantity of data that represent the
+     actual "key". In the case of a keyring, this is a list of keys to which
+     the keyring links; in the case of a user-defined key, it's an arbitrary
+     blob of data.
+
+     Having a payload is not required; and the payload can, in fact, just be a
+     value stored in the struct key itself.
+
+     When a key is instantiated, the key type's instantiation function is
+     called with a blob of data, and that then creates the key's payload in
+     some way.
+
+     Similarly, when userspace wants to read back the contents of the key, if
+     permitted, another key type operation will be called to convert the key's
+     attached payload back into a blob of data.
+
+  *  Each key can be in one of a number of basic states:
+
+      *  Uninstantiated. The key exists, but does not have any data attached.
+     	 Keys being requested from userspace will be in this state.
+
+      *  Instantiated. This is the normal state. The key is fully formed, and
+	 has data attached.
+
+      *  Negative. This is a relatively short-lived state. The key acts as a
+	 note saying that a previous call out to userspace failed, and acts as
+	 a throttle on key lookups. A negative key can be updated to a normal
+	 state.
+
+      *  Expired. Keys can have lifetimes set. If their lifetime is exceeded,
+	 they traverse to this state. An expired key can be updated back to a
+	 normal state.
+
+      *  Revoked. A key is put in this state by userspace action. It can't be
+	 found or operated upon (apart from by unlinking it).
+
+      *  Dead. The key's type was unregistered, and so the key is now useless.
+
+Keys in the last three states are subject to garbage collection.  See the
+section on "Garbage collection".
+
+
+Key Service Overview
+====================
+
+The key service provides a number of features besides keys:
+
+  *  The key service defines three special key types:
+
+     (+) "keyring"
+
+	 Keyrings are special keys that contain a list of other keys. Keyring
+	 lists can be modified using various system calls. Keyrings should not
+	 be given a payload when created.
+
+     (+) "user"
+
+	 A key of this type has a description and a payload that are arbitrary
+	 blobs of data. These can be created, updated and read by userspace,
+	 and aren't intended for use by kernel services.
+
+     (+) "logon"
+
+	 Like a "user" key, a "logon" key has a payload that is an arbitrary
+	 blob of data. It is intended as a place to store secrets which are
+	 accessible to the kernel but not to userspace programs.
+
+	 The description can be arbitrary, but must be prefixed with a non-zero
+	 length string that describes the key "subclass". The subclass is
+	 separated from the rest of the description by a ':'. "logon" keys can
+	 be created and updated from userspace, but the payload is only
+	 readable from kernel space.
+
+  *  Each process subscribes to three keyrings: a thread-specific keyring, a
+     process-specific keyring, and a session-specific keyring.
+
+     The thread-specific keyring is discarded from the child when any sort of
+     clone, fork, vfork or execve occurs. A new keyring is created only when
+     required.
+
+     The process-specific keyring is replaced with an empty one in the child on
+     clone, fork, vfork unless CLONE_THREAD is supplied, in which case it is
+     shared. execve also discards the process's process keyring and creates a
+     new one.
+
+     The session-specific keyring is persistent across clone, fork, vfork and
+     execve, even when the latter executes a set-UID or set-GID binary. A
+     process can, however, replace its current session keyring with a new one
+     by using PR_JOIN_SESSION_KEYRING. It is permitted to request an anonymous
+     new one, or to attempt to create or join one of a specific name.
+
+     The ownership of the thread keyring changes when the real UID and GID of
+     the thread changes.
+
+  *  Each user ID resident in the system holds two special keyrings: a user
+     specific keyring and a default user session keyring. The default session
+     keyring is initialised with a link to the user-specific keyring.
+
+     When a process changes its real UID, if it used to have no session key, it
+     will be subscribed to the default session key for the new UID.
+
+     If a process attempts to access its session key when it doesn't have one,
+     it will be subscribed to the default for its current UID.
+
+  *  Each user has two quotas against which the keys they own are tracked. One
+     limits the total number of keys and keyrings, the other limits the total
+     amount of description and payload space that can be consumed.
+
+     The user can view information on this and other statistics through procfs
+     files.  The root user may also alter the quota limits through sysctl files
+     (see the section "New procfs files").
+
+     Process-specific and thread-specific keyrings are not counted towards a
+     user's quota.
+
+     If a system call that modifies a key or keyring in some way would put the
+     user over quota, the operation is refused and error EDQUOT is returned.
+
+  *  There's a system call interface by which userspace programs can create and
+     manipulate keys and keyrings.
+
+  *  There's a kernel interface by which services can register types and search
+     for keys.
+
+  *  There's a way for the a search done from the kernel to call back to
+     userspace to request a key that can't be found in a process's keyrings.
+
+  *  An optional filesystem is available through which the key database can be
+     viewed and manipulated.
+
+
+Key Access Permissions
+======================
+
+Keys have an owner user ID, a group access ID, and a permissions mask. The mask
+has up to eight bits each for possessor, user, group and other access. Only
+six of each set of eight bits are defined. These permissions granted are:
+
+  *  View
+
+     This permits a key or keyring's attributes to be viewed - including key
+     type and description.
+
+  *  Read
+
+     This permits a key's payload to be viewed or a keyring's list of linked
+     keys.
+
+  *  Write
+
+     This permits a key's payload to be instantiated or updated, or it allows a
+     link to be added to or removed from a keyring.
+
+  *  Search
+
+     This permits keyrings to be searched and keys to be found. Searches can
+     only recurse into nested keyrings that have search permission set.
+
+  *  Link
+
+     This permits a key or keyring to be linked to. To create a link from a
+     keyring to a key, a process must have Write permission on the keyring and
+     Link permission on the key.
+
+  *  Set Attribute
+
+     This permits a key's UID, GID and permissions mask to be changed.
+
+For changing the ownership, group ID or permissions mask, being the owner of
+the key or having the sysadmin capability is sufficient.
+
+
+SELinux Support
+===============
+
+The security class "key" has been added to SELinux so that mandatory access
+controls can be applied to keys created within various contexts.  This support
+is preliminary, and is likely to change quite significantly in the near future.
+Currently, all of the basic permissions explained above are provided in SELinux
+as well; SELinux is simply invoked after all basic permission checks have been
+performed.
+
+The value of the file /proc/self/attr/keycreate influences the labeling of
+newly-created keys.  If the contents of that file correspond to an SELinux
+security context, then the key will be assigned that context.  Otherwise, the
+key will be assigned the current context of the task that invoked the key
+creation request.  Tasks must be granted explicit permission to assign a
+particular context to newly-created keys, using the "create" permission in the
+key security class.
+
+The default keyrings associated with users will be labeled with the default
+context of the user if and only if the login programs have been instrumented to
+properly initialize keycreate during the login process.  Otherwise, they will
+be labeled with the context of the login program itself.
+
+Note, however, that the default keyrings associated with the root user are
+labeled with the default kernel context, since they are created early in the
+boot process, before root has a chance to log in.
+
+The keyrings associated with new threads are each labeled with the context of
+their associated thread, and both session and process keyrings are handled
+similarly.
+
+
+New ProcFS Files
+================
+
+Two files have been added to procfs by which an administrator can find out
+about the status of the key service:
+
+  *  /proc/keys
+
+     This lists the keys that are currently viewable by the task reading the
+     file, giving information about their type, description and permissions.
+     It is not possible to view the payload of the key this way, though some
+     information about it may be given.
+
+     The only keys included in the list are those that grant View permission to
+     the reading process whether or not it possesses them.  Note that LSM
+     security checks are still performed, and may further filter out keys that
+     the current process is not authorised to view.
+
+     The contents of the file look like this::
+
+	SERIAL   FLAGS  USAGE EXPY PERM     UID   GID   TYPE      DESCRIPTION: SUMMARY
+	00000001 I-----    39 perm 1f3f0000     0     0 keyring   _uid_ses.0: 1/4
+	00000002 I-----     2 perm 1f3f0000     0     0 keyring   _uid.0: empty
+	00000007 I-----     1 perm 1f3f0000     0     0 keyring   _pid.1: empty
+	0000018d I-----     1 perm 1f3f0000     0     0 keyring   _pid.412: empty
+	000004d2 I--Q--     1 perm 1f3f0000    32    -1 keyring   _uid.32: 1/4
+	000004d3 I--Q--     3 perm 1f3f0000    32    -1 keyring   _uid_ses.32: empty
+	00000892 I--QU-     1 perm 1f000000     0     0 user      metal:copper: 0
+	00000893 I--Q-N     1  35s 1f3f0000     0     0 user      metal:silver: 0
+	00000894 I--Q--     1  10h 003f0000     0     0 user      metal:gold: 0
+
+     The flags are::
+
+	I	Instantiated
+	R	Revoked
+	D	Dead
+	Q	Contributes to user's quota
+	U	Under construction by callback to userspace
+	N	Negative key
+
+
+  *  /proc/key-users
+
+     This file lists the tracking data for each user that has at least one key
+     on the system.  Such data includes quota information and statistics::
+
+	[root@andromeda root]# cat /proc/key-users
+	0:     46 45/45 1/100 13/10000
+	29:     2 2/2 2/100 40/10000
+	32:     2 2/2 2/100 40/10000
+	38:     2 2/2 2/100 40/10000
+
+     The format of each line is::
+
+	<UID>:			User ID to which this applies
+	<usage>			Structure refcount
+	<inst>/<keys>		Total number of keys and number instantiated
+	<keys>/<max>		Key count quota
+	<bytes>/<max>		Key size quota
+
+
+Four new sysctl files have been added also for the purpose of controlling the
+quota limits on keys:
+
+  *  /proc/sys/kernel/keys/root_maxkeys
+     /proc/sys/kernel/keys/root_maxbytes
+
+     These files hold the maximum number of keys that root may have and the
+     maximum total number of bytes of data that root may have stored in those
+     keys.
+
+  *  /proc/sys/kernel/keys/maxkeys
+     /proc/sys/kernel/keys/maxbytes
+
+     These files hold the maximum number of keys that each non-root user may
+     have and the maximum total number of bytes of data that each of those
+     users may have stored in their keys.
+
+Root may alter these by writing each new limit as a decimal number string to
+the appropriate file.
+
+
+Userspace System Call Interface
+===============================
+
+Userspace can manipulate keys directly through three new syscalls: add_key,
+request_key and keyctl. The latter provides a number of functions for
+manipulating keys.
+
+When referring to a key directly, userspace programs should use the key's
+serial number (a positive 32-bit integer). However, there are some special
+values available for referring to special keys and keyrings that relate to the
+process making the call::
+
+	CONSTANT			VALUE	KEY REFERENCED
+	==============================	======	===========================
+	KEY_SPEC_THREAD_KEYRING		-1	thread-specific keyring
+	KEY_SPEC_PROCESS_KEYRING	-2	process-specific keyring
+	KEY_SPEC_SESSION_KEYRING	-3	session-specific keyring
+	KEY_SPEC_USER_KEYRING		-4	UID-specific keyring
+	KEY_SPEC_USER_SESSION_KEYRING	-5	UID-session keyring
+	KEY_SPEC_GROUP_KEYRING		-6	GID-specific keyring
+	KEY_SPEC_REQKEY_AUTH_KEY	-7	assumed request_key()
+						  authorisation key
+
+
+The main syscalls are:
+
+  *  Create a new key of given type, description and payload and add it to the
+     nominated keyring::
+
+	key_serial_t add_key(const char *type, const char *desc,
+			     const void *payload, size_t plen,
+			     key_serial_t keyring);
+
+     If a key of the same type and description as that proposed already exists
+     in the keyring, this will try to update it with the given payload, or it
+     will return error EEXIST if that function is not supported by the key
+     type. The process must also have permission to write to the key to be able
+     to update it. The new key will have all user permissions granted and no
+     group or third party permissions.
+
+     Otherwise, this will attempt to create a new key of the specified type and
+     description, and to instantiate it with the supplied payload and attach it
+     to the keyring. In this case, an error will be generated if the process
+     does not have permission to write to the keyring.
+
+     If the key type supports it, if the description is NULL or an empty
+     string, the key type will try and generate a description from the content
+     of the payload.
+
+     The payload is optional, and the pointer can be NULL if not required by
+     the type. The payload is plen in size, and plen can be zero for an empty
+     payload.
+
+     A new keyring can be generated by setting type "keyring", the keyring name
+     as the description (or NULL) and setting the payload to NULL.
+
+     User defined keys can be created by specifying type "user". It is
+     recommended that a user defined key's description by prefixed with a type
+     ID and a colon, such as "krb5tgt:" for a Kerberos 5 ticket granting
+     ticket.
+
+     Any other type must have been registered with the kernel in advance by a
+     kernel service such as a filesystem.
+
+     The ID of the new or updated key is returned if successful.
+
+
+  *  Search the process's keyrings for a key, potentially calling out to
+     userspace to create it::
+
+	key_serial_t request_key(const char *type, const char *description,
+				 const char *callout_info,
+				 key_serial_t dest_keyring);
+
+     This function searches all the process's keyrings in the order thread,
+     process, session for a matching key. This works very much like
+     KEYCTL_SEARCH, including the optional attachment of the discovered key to
+     a keyring.
+
+     If a key cannot be found, and if callout_info is not NULL, then
+     /sbin/request-key will be invoked in an attempt to obtain a key. The
+     callout_info string will be passed as an argument to the program.
+
+     To link a key into the destination keyring the key must grant link
+     permission on the key to the caller and the keyring must grant write
+     permission.
+
+     See also Documentation/security/keys/request-key.rst.
+
+
+The keyctl syscall functions are:
+
+  *  Map a special key ID to a real key ID for this process::
+
+	key_serial_t keyctl(KEYCTL_GET_KEYRING_ID, key_serial_t id,
+			    int create);
+
+     The special key specified by "id" is looked up (with the key being created
+     if necessary) and the ID of the key or keyring thus found is returned if
+     it exists.
+
+     If the key does not yet exist, the key will be created if "create" is
+     non-zero; and the error ENOKEY will be returned if "create" is zero.
+
+
+  *  Replace the session keyring this process subscribes to with a new one::
+
+	key_serial_t keyctl(KEYCTL_JOIN_SESSION_KEYRING, const char *name);
+
+     If name is NULL, an anonymous keyring is created attached to the process
+     as its session keyring, displacing the old session keyring.
+
+     If name is not NULL, if a keyring of that name exists, the process
+     attempts to attach it as the session keyring, returning an error if that
+     is not permitted; otherwise a new keyring of that name is created and
+     attached as the session keyring.
+
+     To attach to a named keyring, the keyring must have search permission for
+     the process's ownership.
+
+     The ID of the new session keyring is returned if successful.
+
+
+  *  Update the specified key::
+
+	long keyctl(KEYCTL_UPDATE, key_serial_t key, const void *payload,
+		    size_t plen);
+
+     This will try to update the specified key with the given payload, or it
+     will return error EOPNOTSUPP if that function is not supported by the key
+     type. The process must also have permission to write to the key to be able
+     to update it.
+
+     The payload is of length plen, and may be absent or empty as for
+     add_key().
+
+
+  *  Revoke a key::
+
+	long keyctl(KEYCTL_REVOKE, key_serial_t key);
+
+     This makes a key unavailable for further operations. Further attempts to
+     use the key will be met with error EKEYREVOKED, and the key will no longer
+     be findable.
+
+
+  *  Change the ownership of a key::
+
+	long keyctl(KEYCTL_CHOWN, key_serial_t key, uid_t uid, gid_t gid);
+
+     This function permits a key's owner and group ID to be changed. Either one
+     of uid or gid can be set to -1 to suppress that change.
+
+     Only the superuser can change a key's owner to something other than the
+     key's current owner. Similarly, only the superuser can change a key's
+     group ID to something other than the calling process's group ID or one of
+     its group list members.
+
+
+  *  Change the permissions mask on a key::
+
+	long keyctl(KEYCTL_SETPERM, key_serial_t key, key_perm_t perm);
+
+     This function permits the owner of a key or the superuser to change the
+     permissions mask on a key.
+
+     Only bits the available bits are permitted; if any other bits are set,
+     error EINVAL will be returned.
+
+
+  *  Describe a key::
+
+	long keyctl(KEYCTL_DESCRIBE, key_serial_t key, char *buffer,
+		    size_t buflen);
+
+     This function returns a summary of the key's attributes (but not its
+     payload data) as a string in the buffer provided.
+
+     Unless there's an error, it always returns the amount of data it could
+     produce, even if that's too big for the buffer, but it won't copy more
+     than requested to userspace. If the buffer pointer is NULL then no copy
+     will take place.
+
+     A process must have view permission on the key for this function to be
+     successful.
+
+     If successful, a string is placed in the buffer in the following format::
+
+	<type>;<uid>;<gid>;<perm>;<description>
+
+     Where type and description are strings, uid and gid are decimal, and perm
+     is hexadecimal. A NUL character is included at the end of the string if
+     the buffer is sufficiently big.
+
+     This can be parsed with::
+
+	sscanf(buffer, "%[^;];%d;%d;%o;%s", type, &uid, &gid, &mode, desc);
+
+
+  *  Clear out a keyring::
+
+	long keyctl(KEYCTL_CLEAR, key_serial_t keyring);
+
+     This function clears the list of keys attached to a keyring. The calling
+     process must have write permission on the keyring, and it must be a
+     keyring (or else error ENOTDIR will result).
+
+     This function can also be used to clear special kernel keyrings if they
+     are appropriately marked if the user has CAP_SYS_ADMIN capability.  The
+     DNS resolver cache keyring is an example of this.
+
+
+  *  Link a key into a keyring::
+
+	long keyctl(KEYCTL_LINK, key_serial_t keyring, key_serial_t key);
+
+     This function creates a link from the keyring to the key. The process must
+     have write permission on the keyring and must have link permission on the
+     key.
+
+     Should the keyring not be a keyring, error ENOTDIR will result; and if the
+     keyring is full, error ENFILE will result.
+
+     The link procedure checks the nesting of the keyrings, returning ELOOP if
+     it appears too deep or EDEADLK if the link would introduce a cycle.
+
+     Any links within the keyring to keys that match the new key in terms of
+     type and description will be discarded from the keyring as the new one is
+     added.
+
+
+  *  Move a key from one keyring to another::
+
+	long keyctl(KEYCTL_MOVE,
+		    key_serial_t id,
+		    key_serial_t from_ring_id,
+		    key_serial_t to_ring_id,
+		    unsigned int flags);
+
+     Move the key specified by "id" from the keyring specified by
+     "from_ring_id" to the keyring specified by "to_ring_id".  If the two
+     keyrings are the same, nothing is done.
+
+     "flags" can have KEYCTL_MOVE_EXCL set in it to cause the operation to fail
+     with EEXIST if a matching key exists in the destination keyring, otherwise
+     such a key will be replaced.
+
+     A process must have link permission on the key for this function to be
+     successful and write permission on both keyrings.  Any errors that can
+     occur from KEYCTL_LINK also apply on the destination keyring here.
+
+
+  *  Unlink a key or keyring from another keyring::
+
+	long keyctl(KEYCTL_UNLINK, key_serial_t keyring, key_serial_t key);
+
+     This function looks through the keyring for the first link to the
+     specified key, and removes it if found. Subsequent links to that key are
+     ignored. The process must have write permission on the keyring.
+
+     If the keyring is not a keyring, error ENOTDIR will result; and if the key
+     is not present, error ENOENT will be the result.
+
+
+  *  Search a keyring tree for a key::
+
+	key_serial_t keyctl(KEYCTL_SEARCH, key_serial_t keyring,
+			    const char *type, const char *description,
+			    key_serial_t dest_keyring);
+
+     This searches the keyring tree headed by the specified keyring until a key
+     is found that matches the type and description criteria. Each keyring is
+     checked for keys before recursion into its children occurs.
+
+     The process must have search permission on the top level keyring, or else
+     error EACCES will result. Only keyrings that the process has search
+     permission on will be recursed into, and only keys and keyrings for which
+     a process has search permission can be matched. If the specified keyring
+     is not a keyring, ENOTDIR will result.
+
+     If the search succeeds, the function will attempt to link the found key
+     into the destination keyring if one is supplied (non-zero ID). All the
+     constraints applicable to KEYCTL_LINK apply in this case too.
+
+     Error ENOKEY, EKEYREVOKED or EKEYEXPIRED will be returned if the search
+     fails. On success, the resulting key ID will be returned.
+
+
+  *  Read the payload data from a key::
+
+	long keyctl(KEYCTL_READ, key_serial_t keyring, char *buffer,
+		    size_t buflen);
+
+     This function attempts to read the payload data from the specified key
+     into the buffer. The process must have read permission on the key to
+     succeed.
+
+     The returned data will be processed for presentation by the key type. For
+     instance, a keyring will return an array of key_serial_t entries
+     representing the IDs of all the keys to which it is subscribed. The user
+     defined key type will return its data as is. If a key type does not
+     implement this function, error EOPNOTSUPP will result.
+
+     If the specified buffer is too small, then the size of the buffer required
+     will be returned.  Note that in this case, the contents of the buffer may
+     have been overwritten in some undefined way.
+
+     Otherwise, on success, the function will return the amount of data copied
+     into the buffer.
+
+  *  Instantiate a partially constructed key::
+
+	long keyctl(KEYCTL_INSTANTIATE, key_serial_t key,
+		    const void *payload, size_t plen,
+		    key_serial_t keyring);
+	long keyctl(KEYCTL_INSTANTIATE_IOV, key_serial_t key,
+		    const struct iovec *payload_iov, unsigned ioc,
+		    key_serial_t keyring);
+
+     If the kernel calls back to userspace to complete the instantiation of a
+     key, userspace should use this call to supply data for the key before the
+     invoked process returns, or else the key will be marked negative
+     automatically.
+
+     The process must have write access on the key to be able to instantiate
+     it, and the key must be uninstantiated.
+
+     If a keyring is specified (non-zero), the key will also be linked into
+     that keyring, however all the constraints applying in KEYCTL_LINK apply in
+     this case too.
+
+     The payload and plen arguments describe the payload data as for add_key().
+
+     The payload_iov and ioc arguments describe the payload data in an iovec
+     array instead of a single buffer.
+
+
+  *  Negatively instantiate a partially constructed key::
+
+	long keyctl(KEYCTL_NEGATE, key_serial_t key,
+		    unsigned timeout, key_serial_t keyring);
+	long keyctl(KEYCTL_REJECT, key_serial_t key,
+		    unsigned timeout, unsigned error, key_serial_t keyring);
+
+     If the kernel calls back to userspace to complete the instantiation of a
+     key, userspace should use this call mark the key as negative before the
+     invoked process returns if it is unable to fulfill the request.
+
+     The process must have write access on the key to be able to instantiate
+     it, and the key must be uninstantiated.
+
+     If a keyring is specified (non-zero), the key will also be linked into
+     that keyring, however all the constraints applying in KEYCTL_LINK apply in
+     this case too.
+
+     If the key is rejected, future searches for it will return the specified
+     error code until the rejected key expires.  Negating the key is the same
+     as rejecting the key with ENOKEY as the error code.
+
+
+  *  Set the default request-key destination keyring::
+
+	long keyctl(KEYCTL_SET_REQKEY_KEYRING, int reqkey_defl);
+
+     This sets the default keyring to which implicitly requested keys will be
+     attached for this thread. reqkey_defl should be one of these constants::
+
+	CONSTANT				VALUE	NEW DEFAULT KEYRING
+	======================================	======	=======================
+	KEY_REQKEY_DEFL_NO_CHANGE		-1	No change
+	KEY_REQKEY_DEFL_DEFAULT			0	Default[1]
+	KEY_REQKEY_DEFL_THREAD_KEYRING		1	Thread keyring
+	KEY_REQKEY_DEFL_PROCESS_KEYRING		2	Process keyring
+	KEY_REQKEY_DEFL_SESSION_KEYRING		3	Session keyring
+	KEY_REQKEY_DEFL_USER_KEYRING		4	User keyring
+	KEY_REQKEY_DEFL_USER_SESSION_KEYRING	5	User session keyring
+	KEY_REQKEY_DEFL_GROUP_KEYRING		6	Group keyring
+
+     The old default will be returned if successful and error EINVAL will be
+     returned if reqkey_defl is not one of the above values.
+
+     The default keyring can be overridden by the keyring indicated to the
+     request_key() system call.
+
+     Note that this setting is inherited across fork/exec.
+
+     [1] The default is: the thread keyring if there is one, otherwise
+     the process keyring if there is one, otherwise the session keyring if
+     there is one, otherwise the user default session keyring.
+
+
+  *  Set the timeout on a key::
+
+	long keyctl(KEYCTL_SET_TIMEOUT, key_serial_t key, unsigned timeout);
+
+     This sets or clears the timeout on a key. The timeout can be 0 to clear
+     the timeout or a number of seconds to set the expiry time that far into
+     the future.
+
+     The process must have attribute modification access on a key to set its
+     timeout. Timeouts may not be set with this function on negative, revoked
+     or expired keys.
+
+
+  *  Assume the authority granted to instantiate a key::
+
+	long keyctl(KEYCTL_ASSUME_AUTHORITY, key_serial_t key);
+
+     This assumes or divests the authority required to instantiate the
+     specified key. Authority can only be assumed if the thread has the
+     authorisation key associated with the specified key in its keyrings
+     somewhere.
+
+     Once authority is assumed, searches for keys will also search the
+     requester's keyrings using the requester's security label, UID, GID and
+     groups.
+
+     If the requested authority is unavailable, error EPERM will be returned,
+     likewise if the authority has been revoked because the target key is
+     already instantiated.
+
+     If the specified key is 0, then any assumed authority will be divested.
+
+     The assumed authoritative key is inherited across fork and exec.
+
+
+  *  Get the LSM security context attached to a key::
+
+	long keyctl(KEYCTL_GET_SECURITY, key_serial_t key, char *buffer,
+		    size_t buflen)
+
+     This function returns a string that represents the LSM security context
+     attached to a key in the buffer provided.
+
+     Unless there's an error, it always returns the amount of data it could
+     produce, even if that's too big for the buffer, but it won't copy more
+     than requested to userspace. If the buffer pointer is NULL then no copy
+     will take place.
+
+     A NUL character is included at the end of the string if the buffer is
+     sufficiently big.  This is included in the returned count.  If no LSM is
+     in force then an empty string will be returned.
+
+     A process must have view permission on the key for this function to be
+     successful.
+
+
+  *  Install the calling process's session keyring on its parent::
+
+	long keyctl(KEYCTL_SESSION_TO_PARENT);
+
+     This functions attempts to install the calling process's session keyring
+     on to the calling process's parent, replacing the parent's current session
+     keyring.
+
+     The calling process must have the same ownership as its parent, the
+     keyring must have the same ownership as the calling process, the calling
+     process must have LINK permission on the keyring and the active LSM module
+     mustn't deny permission, otherwise error EPERM will be returned.
+
+     Error ENOMEM will be returned if there was insufficient memory to complete
+     the operation, otherwise 0 will be returned to indicate success.
+
+     The keyring will be replaced next time the parent process leaves the
+     kernel and resumes executing userspace.
+
+
+  *  Invalidate a key::
+
+	long keyctl(KEYCTL_INVALIDATE, key_serial_t key);
+
+     This function marks a key as being invalidated and then wakes up the
+     garbage collector.  The garbage collector immediately removes invalidated
+     keys from all keyrings and deletes the key when its reference count
+     reaches zero.
+
+     Keys that are marked invalidated become invisible to normal key operations
+     immediately, though they are still visible in /proc/keys until deleted
+     (they're marked with an 'i' flag).
+
+     A process must have search permission on the key for this function to be
+     successful.
+
+  *  Compute a Diffie-Hellman shared secret or public key::
+
+	long keyctl(KEYCTL_DH_COMPUTE, struct keyctl_dh_params *params,
+		    char *buffer, size_t buflen, struct keyctl_kdf_params *kdf);
+
+     The params struct contains serial numbers for three keys::
+
+	 - The prime, p, known to both parties
+	 - The local private key
+	 - The base integer, which is either a shared generator or the
+	   remote public key
+
+     The value computed is::
+
+	result = base ^ private (mod prime)
+
+     If the base is the shared generator, the result is the local
+     public key.  If the base is the remote public key, the result is
+     the shared secret.
+
+     If the parameter kdf is NULL, the following applies:
+
+	 - The buffer length must be at least the length of the prime, or zero.
+
+	 - If the buffer length is nonzero, the length of the result is
+	   returned when it is successfully calculated and copied in to the
+	   buffer. When the buffer length is zero, the minimum required
+	   buffer length is returned.
+
+     The kdf parameter allows the caller to apply a key derivation function
+     (KDF) on the Diffie-Hellman computation where only the result
+     of the KDF is returned to the caller. The KDF is characterized with
+     struct keyctl_kdf_params as follows:
+
+	 - ``char *hashname`` specifies the NUL terminated string identifying
+	   the hash used from the kernel crypto API and applied for the KDF
+	   operation. The KDF implementation complies with SP800-56A as well
+	   as with SP800-108 (the counter KDF).
+
+	 - ``char *otherinfo`` specifies the OtherInfo data as documented in
+	   SP800-56A section 5.8.1.2. The length of the buffer is given with
+	   otherinfolen. The format of OtherInfo is defined by the caller.
+	   The otherinfo pointer may be NULL if no OtherInfo shall be used.
+
+     This function will return error EOPNOTSUPP if the key type is not
+     supported, error ENOKEY if the key could not be found, or error
+     EACCES if the key is not readable by the caller. In addition, the
+     function will return EMSGSIZE when the parameter kdf is non-NULL
+     and either the buffer length or the OtherInfo length exceeds the
+     allowed length.
+
+
+  *  Restrict keyring linkage::
+
+	long keyctl(KEYCTL_RESTRICT_KEYRING, key_serial_t keyring,
+		    const char *type, const char *restriction);
+
+     An existing keyring can restrict linkage of additional keys by evaluating
+     the contents of the key according to a restriction scheme.
+
+     "keyring" is the key ID for an existing keyring to apply a restriction
+     to. It may be empty or may already have keys linked. Existing linked keys
+     will remain in the keyring even if the new restriction would reject them.
+
+     "type" is a registered key type.
+
+     "restriction" is a string describing how key linkage is to be restricted.
+     The format varies depending on the key type, and the string is passed to
+     the lookup_restriction() function for the requested type.  It may specify
+     a method and relevant data for the restriction such as signature
+     verification or constraints on key payload. If the requested key type is
+     later unregistered, no keys may be added to the keyring after the key type
+     is removed.
+
+     To apply a keyring restriction the process must have Set Attribute
+     permission and the keyring must not be previously restricted.
+
+     One application of restricted keyrings is to verify X.509 certificate
+     chains or individual certificate signatures using the asymmetric key type.
+     See Documentation/crypto/asymmetric-keys.rst for specific restrictions
+     applicable to the asymmetric key type.
+
+
+  *  Query an asymmetric key::
+
+	long keyctl(KEYCTL_PKEY_QUERY,
+		    key_serial_t key_id, unsigned long reserved,
+		    const char *params,
+		    struct keyctl_pkey_query *info);
+
+     Get information about an asymmetric key.  Specific algorithms and
+     encodings may be queried by using the ``params`` argument.  This is a
+     string containing a space- or tab-separated string of key-value pairs.
+     Currently supported keys include ``enc`` and ``hash``.  The information
+     is returned in the keyctl_pkey_query struct::
+
+	__u32	supported_ops;
+	__u32	key_size;
+	__u16	max_data_size;
+	__u16	max_sig_size;
+	__u16	max_enc_size;
+	__u16	max_dec_size;
+	__u32	__spare[10];
+
+     ``supported_ops`` contains a bit mask of flags indicating which ops are
+     supported.  This is constructed from a bitwise-OR of::
+
+	KEYCTL_SUPPORTS_{ENCRYPT,DECRYPT,SIGN,VERIFY}
+
+     ``key_size`` indicated the size of the key in bits.
+
+     ``max_*_size`` indicate the maximum sizes in bytes of a blob of data to be
+     signed, a signature blob, a blob to be encrypted and a blob to be
+     decrypted.
+
+     ``__spare[]`` must be set to 0.  This is intended for future use to hand
+     over one or more passphrases needed unlock a key.
+
+     If successful, 0 is returned.  If the key is not an asymmetric key,
+     EOPNOTSUPP is returned.
+
+
+  *  Encrypt, decrypt, sign or verify a blob using an asymmetric key::
+
+	long keyctl(KEYCTL_PKEY_ENCRYPT,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_DECRYPT,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_SIGN,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_VERIFY,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    const void *in2);
+
+     Use an asymmetric key to perform a public-key cryptographic operation a
+     blob of data.  For encryption and verification, the asymmetric key may
+     only need the public parts to be available, but for decryption and signing
+     the private parts are required also.
+
+     The parameter block pointed to by params contains a number of integer
+     values::
+
+	__s32		key_id;
+	__u32		in_len;
+	__u32		out_len;
+	__u32		in2_len;
+
+     ``key_id`` is the ID of the asymmetric key to be used.  ``in_len`` and
+     ``in2_len`` indicate the amount of data in the in and in2 buffers and
+     ``out_len`` indicates the size of the out buffer as appropriate for the
+     above operations.
+
+     For a given operation, the in and out buffers are used as follows::
+
+	Operation ID		in,in_len	out,out_len	in2,in2_len
+	=======================	===============	===============	===============
+	KEYCTL_PKEY_ENCRYPT	Raw data	Encrypted data	-
+	KEYCTL_PKEY_DECRYPT	Encrypted data	Raw data	-
+	KEYCTL_PKEY_SIGN	Raw data	Signature	-
+	KEYCTL_PKEY_VERIFY	Raw data	-		Signature
+
+     ``info`` is a string of key=value pairs that supply supplementary
+     information.  These include:
+
+	``enc=<encoding>`` The encoding of the encrypted/signature blob.  This
+			can be "pkcs1" for RSASSA-PKCS1-v1.5 or
+			RSAES-PKCS1-v1.5; "pss" for "RSASSA-PSS"; "oaep" for
+			"RSAES-OAEP".  If omitted or is "raw", the raw output
+			of the encryption function is specified.
+
+	``hash=<algo>``	If the data buffer contains the output of a hash
+			function and the encoding includes some indication of
+			which hash function was used, the hash function can be
+			specified with this, eg. "hash=sha256".
+
+     The ``__spare[]`` space in the parameter block must be set to 0.  This is
+     intended, amongst other things, to allow the passing of passphrases
+     required to unlock a key.
+
+     If successful, encrypt, decrypt and sign all return the amount of data
+     written into the output buffer.  Verification returns 0 on success.
+
+
+  *  Watch a key or keyring for changes::
+
+	long keyctl(KEYCTL_WATCH_KEY, key_serial_t key, int queue_fd,
+		    const struct watch_notification_filter *filter);
+
+     This will set or remove a watch for changes on the specified key or
+     keyring.
+
+     "key" is the ID of the key to be watched.
+
+     "queue_fd" is a file descriptor referring to an open pipe which
+     manages the buffer into which notifications will be delivered.
+
+     "filter" is either NULL to remove a watch or a filter specification to
+     indicate what events are required from the key.
+
+     See Documentation/core-api/watch_queue.rst for more information.
+
+     Note that only one watch may be emplaced for any particular { key,
+     queue_fd } combination.
+
+     Notification records look like::
+
+	struct key_notification {
+		struct watch_notification watch;
+		__u32	key_id;
+		__u32	aux;
+	};
+
+     In this, watch::type will be "WATCH_TYPE_KEY_NOTIFY" and subtype will be
+     one of::
+
+	NOTIFY_KEY_INSTANTIATED
+	NOTIFY_KEY_UPDATED
+	NOTIFY_KEY_LINKED
+	NOTIFY_KEY_UNLINKED
+	NOTIFY_KEY_CLEARED
+	NOTIFY_KEY_REVOKED
+	NOTIFY_KEY_INVALIDATED
+	NOTIFY_KEY_SETATTR
+
+     Where these indicate a key being instantiated/rejected, updated, a link
+     being made in a keyring, a link being removed from a keyring, a keyring
+     being cleared, a key being revoked, a key being invalidated or a key
+     having one of its attributes changed (user, group, perm, timeout,
+     restriction).
+
+     If a watched key is deleted, a basic watch_notification will be issued
+     with "type" set to WATCH_TYPE_META and "subtype" set to
+     watch_meta_removal_notification.  The watchpoint ID will be set in the
+     "info" field.
+
+     This needs to be configured by enabling:
+
+	"Provide key/keyring change notifications" (KEY_NOTIFICATIONS)
+
+
+Kernel Services
+===============
+
+The kernel services for key management are fairly simple to deal with. They can
+be broken down into two areas: keys and key types.
+
+Dealing with keys is fairly straightforward. Firstly, the kernel service
+registers its type, then it searches for a key of that type. It should retain
+the key as long as it has need of it, and then it should release it. For a
+filesystem or device file, a search would probably be performed during the open
+call, and the key released upon close. How to deal with conflicting keys due to
+two different users opening the same file is left to the filesystem author to
+solve.
+
+To access the key manager, the following header must be #included::
+
+	<linux/key.h>
+
+Specific key types should have a header file under include/keys/ that should be
+used to access that type.  For keys of type "user", for example, that would be::
+
+	<keys/user-type.h>
+
+Note that there are two different types of pointers to keys that may be
+encountered:
+
+  *  struct key *
+
+     This simply points to the key structure itself. Key structures will be at
+     least four-byte aligned.
+
+  *  key_ref_t
+
+     This is equivalent to a ``struct key *``, but the least significant bit is set
+     if the caller "possesses" the key. By "possession" it is meant that the
+     calling processes has a searchable link to the key from one of its
+     keyrings. There are three functions for dealing with these::
+
+	key_ref_t make_key_ref(const struct key *key, bool possession);
+
+	struct key *key_ref_to_ptr(const key_ref_t key_ref);
+
+	bool is_key_possessed(const key_ref_t key_ref);
+
+     The first function constructs a key reference from a key pointer and
+     possession information (which must be true or false).
+
+     The second function retrieves the key pointer from a reference and the
+     third retrieves the possession flag.
+
+When accessing a key's payload contents, certain precautions must be taken to
+prevent access vs modification races. See the section "Notes on accessing
+payload contents" for more information.
+
+ *  To search for a key, call::
+
+	struct key *request_key(const struct key_type *type,
+				const char *description,
+				const char *callout_info);
+
+    This is used to request a key or keyring with a description that matches
+    the description specified according to the key type's match_preparse()
+    method. This permits approximate matching to occur. If callout_string is
+    not NULL, then /sbin/request-key will be invoked in an attempt to obtain
+    the key from userspace. In that case, callout_string will be passed as an
+    argument to the program.
+
+    Should the function fail error ENOKEY, EKEYEXPIRED or EKEYREVOKED will be
+    returned.
+
+    If successful, the key will have been attached to the default keyring for
+    implicitly obtained request-key keys, as set by KEYCTL_SET_REQKEY_KEYRING.
+
+    See also Documentation/security/keys/request-key.rst.
+
+
+ *  To search for a key in a specific domain, call::
+
+	struct key *request_key_tag(const struct key_type *type,
+				    const char *description,
+				    struct key_tag *domain_tag,
+				    const char *callout_info);
+
+    This is identical to request_key(), except that a domain tag may be
+    specifies that causes search algorithm to only match keys matching that
+    tag.  The domain_tag may be NULL, specifying a global domain that is
+    separate from any nominated domain.
+
+
+ *  To search for a key, passing auxiliary data to the upcaller, call::
+
+	struct key *request_key_with_auxdata(const struct key_type *type,
+					     const char *description,
+					     struct key_tag *domain_tag,
+					     const void *callout_info,
+					     size_t callout_len,
+					     void *aux);
+
+    This is identical to request_key_tag(), except that the auxiliary data is
+    passed to the key_type->request_key() op if it exists, and the
+    callout_info is a blob of length callout_len, if given (the length may be
+    0).
+
+
+ *  To search for a key under RCU conditions, call::
+
+	struct key *request_key_rcu(const struct key_type *type,
+				    const char *description,
+				    struct key_tag *domain_tag);
+
+    which is similar to request_key_tag() except that it does not check for
+    keys that are under construction and it will not call out to userspace to
+    construct a key if it can't find a match.
+
+
+ *  When it is no longer required, the key should be released using::
+
+	void key_put(struct key *key);
+
+    Or::
+
+	void key_ref_put(key_ref_t key_ref);
+
+    These can be called from interrupt context. If CONFIG_KEYS is not set then
+    the argument will not be parsed.
+
+
+ *  Extra references can be made to a key by calling one of the following
+    functions::
+
+	struct key *__key_get(struct key *key);
+	struct key *key_get(struct key *key);
+
+    Keys so references will need to be disposed of by calling key_put() when
+    they've been finished with.  The key pointer passed in will be returned.
+
+    In the case of key_get(), if the pointer is NULL or CONFIG_KEYS is not set
+    then the key will not be dereferenced and no increment will take place.
+
+
+ *  A key's serial number can be obtained by calling::
+
+	key_serial_t key_serial(struct key *key);
+
+    If key is NULL or if CONFIG_KEYS is not set then 0 will be returned (in the
+    latter case without parsing the argument).
+
+
+ *  If a keyring was found in the search, this can be further searched by::
+
+	key_ref_t keyring_search(key_ref_t keyring_ref,
+				 const struct key_type *type,
+				 const char *description,
+				 bool recurse)
+
+    This searches the specified keyring only (recurse == false) or keyring tree
+    (recurse == true) specified for a matching key. Error ENOKEY is returned
+    upon failure (use IS_ERR/PTR_ERR to determine). If successful, the returned
+    key will need to be released.
+
+    The possession attribute from the keyring reference is used to control
+    access through the permissions mask and is propagated to the returned key
+    reference pointer if successful.
+
+
+ *  A keyring can be created by::
+
+	struct key *keyring_alloc(const char *description, uid_t uid, gid_t gid,
+				  const struct cred *cred,
+				  key_perm_t perm,
+				  struct key_restriction *restrict_link,
+				  unsigned long flags,
+				  struct key *dest);
+
+    This creates a keyring with the given attributes and returns it.  If dest
+    is not NULL, the new keyring will be linked into the keyring to which it
+    points.  No permission checks are made upon the destination keyring.
+
+    Error EDQUOT can be returned if the keyring would overload the quota (pass
+    KEY_ALLOC_NOT_IN_QUOTA in flags if the keyring shouldn't be accounted
+    towards the user's quota).  Error ENOMEM can also be returned.
+
+    If restrict_link is not NULL, it should point to a structure that contains
+    the function that will be called each time an attempt is made to link a
+    key into the new keyring.  The structure may also contain a key pointer
+    and an associated key type.  The function is called to check whether a key
+    may be added into the keyring or not.  The key type is used by the garbage
+    collector to clean up function or data pointers in this structure if the
+    given key type is unregistered.  Callers of key_create_or_update() within
+    the kernel can pass KEY_ALLOC_BYPASS_RESTRICTION to suppress the check.
+    An example of using this is to manage rings of cryptographic keys that are
+    set up when the kernel boots where userspace is also permitted to add keys
+    - provided they can be verified by a key the kernel already has.
+
+    When called, the restriction function will be passed the keyring being
+    added to, the key type, the payload of the key being added, and data to be
+    used in the restriction check.  Note that when a new key is being created,
+    this is called between payload preparsing and actual key creation.  The
+    function should return 0 to allow the link or an error to reject it.
+
+    A convenience function, restrict_link_reject, exists to always return
+    -EPERM to in this case.
+
+
+ *  To check the validity of a key, this function can be called::
+
+	int validate_key(struct key *key);
+
+    This checks that the key in question hasn't expired or and hasn't been
+    revoked. Should the key be invalid, error EKEYEXPIRED or EKEYREVOKED will
+    be returned. If the key is NULL or if CONFIG_KEYS is not set then 0 will be
+    returned (in the latter case without parsing the argument).
+
+
+ *  To register a key type, the following function should be called::
+
+	int register_key_type(struct key_type *type);
+
+    This will return error EEXIST if a type of the same name is already
+    present.
+
+
+ *  To unregister a key type, call::
+
+	void unregister_key_type(struct key_type *type);
+
+
+Under some circumstances, it may be desirable to deal with a bundle of keys.
+The facility provides access to the keyring type for managing such a bundle::
+
+	struct key_type key_type_keyring;
+
+This can be used with a function such as request_key() to find a specific
+keyring in a process's keyrings.  A keyring thus found can then be searched
+with keyring_search().  Note that it is not possible to use request_key() to
+search a specific keyring, so using keyrings in this way is of limited utility.
+
+
+Notes On Accessing Payload Contents
+===================================
+
+The simplest payload is just data stored in key->payload directly.  In this
+case, there's no need to indulge in RCU or locking when accessing the payload.
+
+More complex payload contents must be allocated and pointers to them set in the
+key->payload.data[] array.  One of the following ways must be selected to
+access the data:
+
+  1) Unmodifiable key type.
+
+     If the key type does not have a modify method, then the key's payload can
+     be accessed without any form of locking, provided that it's known to be
+     instantiated (uninstantiated keys cannot be "found").
+
+  2) The key's semaphore.
+
+     The semaphore could be used to govern access to the payload and to control
+     the payload pointer. It must be write-locked for modifications and would
+     have to be read-locked for general access. The disadvantage of doing this
+     is that the accessor may be required to sleep.
+
+  3) RCU.
+
+     RCU must be used when the semaphore isn't already held; if the semaphore
+     is held then the contents can't change under you unexpectedly as the
+     semaphore must still be used to serialise modifications to the key. The
+     key management code takes care of this for the key type.
+
+     However, this means using::
+
+	rcu_read_lock() ... rcu_dereference() ... rcu_read_unlock()
+
+     to read the pointer, and::
+
+	rcu_dereference() ... rcu_assign_pointer() ... call_rcu()
+
+     to set the pointer and dispose of the old contents after a grace period.
+     Note that only the key type should ever modify a key's payload.
+
+     Furthermore, an RCU controlled payload must hold a struct rcu_head for the
+     use of call_rcu() and, if the payload is of variable size, the length of
+     the payload. key->datalen cannot be relied upon to be consistent with the
+     payload just dereferenced if the key's semaphore is not held.
+
+     Note that key->payload.data[0] has a shadow that is marked for __rcu
+     usage.  This is called key->payload.rcu_data0.  The following accessors
+     wrap the RCU calls to this element:
+
+     a) Set or change the first payload pointer::
+
+		rcu_assign_keypointer(struct key *key, void *data);
+
+     b) Read the first payload pointer with the key semaphore held::
+
+		[const] void *dereference_key_locked([const] struct key *key);
+
+	 Note that the return value will inherit its constness from the key
+	 parameter.  Static analysis will give an error if it things the lock
+	 isn't held.
+
+     c) Read the first payload pointer with the RCU read lock held::
+
+		const void *dereference_key_rcu(const struct key *key);
+
+
+Defining a Key Type
+===================
+
+A kernel service may want to define its own key type. For instance, an AFS
+filesystem might want to define a Kerberos 5 ticket key type. To do this, it
+author fills in a key_type struct and registers it with the system.
+
+Source files that implement key types should include the following header file::
+
+	<linux/key-type.h>
+
+The structure has a number of fields, some of which are mandatory:
+
+  *  ``const char *name``
+
+     The name of the key type. This is used to translate a key type name
+     supplied by userspace into a pointer to the structure.
+
+
+  *  ``size_t def_datalen``
+
+     This is optional - it supplies the default payload data length as
+     contributed to the quota. If the key type's payload is always or almost
+     always the same size, then this is a more efficient way to do things.
+
+     The data length (and quota) on a particular key can always be changed
+     during instantiation or update by calling::
+
+	int key_payload_reserve(struct key *key, size_t datalen);
+
+     With the revised data length. Error EDQUOT will be returned if this is not
+     viable.
+
+
+  *  ``int (*vet_description)(const char *description);``
+
+     This optional method is called to vet a key description.  If the key type
+     doesn't approve of the key description, it may return an error, otherwise
+     it should return 0.
+
+
+  *  ``int (*preparse)(struct key_preparsed_payload *prep);``
+
+     This optional method permits the key type to attempt to parse payload
+     before a key is created (add key) or the key semaphore is taken (update or
+     instantiate key).  The structure pointed to by prep looks like::
+
+	struct key_preparsed_payload {
+		char		*description;
+		union key_payload payload;
+		const void	*data;
+		size_t		datalen;
+		size_t		quotalen;
+		time_t		expiry;
+	};
+
+     Before calling the method, the caller will fill in data and datalen with
+     the payload blob parameters; quotalen will be filled in with the default
+     quota size from the key type; expiry will be set to TIME_T_MAX and the
+     rest will be cleared.
+
+     If a description can be proposed from the payload contents, that should be
+     attached as a string to the description field.  This will be used for the
+     key description if the caller of add_key() passes NULL or "".
+
+     The method can attach anything it likes to payload.  This is merely passed
+     along to the instantiate() or update() operations.  If set, the expiry
+     time will be applied to the key if it is instantiated from this data.
+
+     The method should return 0 if successful or a negative error code
+     otherwise.
+
+
+  *  ``void (*free_preparse)(struct key_preparsed_payload *prep);``
+
+     This method is only required if the preparse() method is provided,
+     otherwise it is unused.  It cleans up anything attached to the description
+     and payload fields of the key_preparsed_payload struct as filled in by the
+     preparse() method.  It will always be called after preparse() returns
+     successfully, even if instantiate() or update() succeed.
+
+
+  *  ``int (*instantiate)(struct key *key, struct key_preparsed_payload *prep);``
+
+     This method is called to attach a payload to a key during construction.
+     The payload attached need not bear any relation to the data passed to this
+     function.
+
+     The prep->data and prep->datalen fields will define the original payload
+     blob.  If preparse() was supplied then other fields may be filled in also.
+
+     If the amount of data attached to the key differs from the size in
+     keytype->def_datalen, then key_payload_reserve() should be called.
+
+     This method does not have to lock the key in order to attach a payload.
+     The fact that KEY_FLAG_INSTANTIATED is not set in key->flags prevents
+     anything else from gaining access to the key.
+
+     It is safe to sleep in this method.
+
+     generic_key_instantiate() is provided to simply copy the data from
+     prep->payload.data[] to key->payload.data[], with RCU-safe assignment on
+     the first element.  It will then clear prep->payload.data[] so that the
+     free_preparse method doesn't release the data.
+
+
+  *  ``int (*update)(struct key *key, const void *data, size_t datalen);``
+
+     If this type of key can be updated, then this method should be provided.
+     It is called to update a key's payload from the blob of data provided.
+
+     The prep->data and prep->datalen fields will define the original payload
+     blob.  If preparse() was supplied then other fields may be filled in also.
+
+     key_payload_reserve() should be called if the data length might change
+     before any changes are actually made. Note that if this succeeds, the type
+     is committed to changing the key because it's already been altered, so all
+     memory allocation must be done first.
+
+     The key will have its semaphore write-locked before this method is called,
+     but this only deters other writers; any changes to the key's payload must
+     be made under RCU conditions, and call_rcu() must be used to dispose of
+     the old payload.
+
+     key_payload_reserve() should be called before the changes are made, but
+     after all allocations and other potentially failing function calls are
+     made.
+
+     It is safe to sleep in this method.
+
+
+  *  ``int (*match_preparse)(struct key_match_data *match_data);``
+
+     This method is optional.  It is called when a key search is about to be
+     performed.  It is given the following structure::
+
+	struct key_match_data {
+		bool (*cmp)(const struct key *key,
+			    const struct key_match_data *match_data);
+		const void	*raw_data;
+		void		*preparsed;
+		unsigned	lookup_type;
+	};
+
+     On entry, raw_data will be pointing to the criteria to be used in matching
+     a key by the caller and should not be modified.  ``(*cmp)()`` will be pointing
+     to the default matcher function (which does an exact description match
+     against raw_data) and lookup_type will be set to indicate a direct lookup.
+
+     The following lookup_type values are available:
+
+       *  KEYRING_SEARCH_LOOKUP_DIRECT - A direct lookup hashes the type and
+      	  description to narrow down the search to a small number of keys.
+
+       *  KEYRING_SEARCH_LOOKUP_ITERATE - An iterative lookup walks all the
+      	  keys in the keyring until one is matched.  This must be used for any
+      	  search that's not doing a simple direct match on the key description.
+
+     The method may set cmp to point to a function of its choice that does some
+     other form of match, may set lookup_type to KEYRING_SEARCH_LOOKUP_ITERATE
+     and may attach something to the preparsed pointer for use by ``(*cmp)()``.
+     ``(*cmp)()`` should return true if a key matches and false otherwise.
+
+     If preparsed is set, it may be necessary to use the match_free() method to
+     clean it up.
+
+     The method should return 0 if successful or a negative error code
+     otherwise.
+
+     It is permitted to sleep in this method, but ``(*cmp)()`` may not sleep as
+     locks will be held over it.
+
+     If match_preparse() is not provided, keys of this type will be matched
+     exactly by their description.
+
+
+  *  ``void (*match_free)(struct key_match_data *match_data);``
+
+     This method is optional.  If given, it called to clean up
+     match_data->preparsed after a successful call to match_preparse().
+
+
+  *  ``void (*revoke)(struct key *key);``
+
+     This method is optional.  It is called to discard part of the payload
+     data upon a key being revoked.  The caller will have the key semaphore
+     write-locked.
+
+     It is safe to sleep in this method, though care should be taken to avoid
+     a deadlock against the key semaphore.
+
+
+  *  ``void (*destroy)(struct key *key);``
+
+     This method is optional. It is called to discard the payload data on a key
+     when it is being destroyed.
+
+     This method does not need to lock the key to access the payload; it can
+     consider the key as being inaccessible at this time. Note that the key's
+     type may have been changed before this function is called.
+
+     It is not safe to sleep in this method; the caller may hold spinlocks.
+
+
+  *  ``void (*describe)(const struct key *key, struct seq_file *p);``
+
+     This method is optional. It is called during /proc/keys reading to
+     summarise a key's description and payload in text form.
+
+     This method will be called with the RCU read lock held. rcu_dereference()
+     should be used to read the payload pointer if the payload is to be
+     accessed. key->datalen cannot be trusted to stay consistent with the
+     contents of the payload.
+
+     The description will not change, though the key's state may.
+
+     It is not safe to sleep in this method; the RCU read lock is held by the
+     caller.
+
+
+  *  ``long (*read)(const struct key *key, char __user *buffer, size_t buflen);``
+
+     This method is optional. It is called by KEYCTL_READ to translate the
+     key's payload into something a blob of data for userspace to deal with.
+     Ideally, the blob should be in the same format as that passed in to the
+     instantiate and update methods.
+
+     If successful, the blob size that could be produced should be returned
+     rather than the size copied.
+
+     This method will be called with the key's semaphore read-locked. This will
+     prevent the key's payload changing. It is not necessary to use RCU locking
+     when accessing the key's payload. It is safe to sleep in this method, such
+     as might happen when the userspace buffer is accessed.
+
+
+  *  ``int (*request_key)(struct key_construction *cons, const char *op, void *aux);``
+
+     This method is optional.  If provided, request_key() and friends will
+     invoke this function rather than upcalling to /sbin/request-key to operate
+     upon a key of this type.
+
+     The aux parameter is as passed to request_key_async_with_auxdata() and
+     similar or is NULL otherwise.  Also passed are the construction record for
+     the key to be operated upon and the operation type (currently only
+     "create").
+
+     This method is permitted to return before the upcall is complete, but the
+     following function must be called under all circumstances to complete the
+     instantiation process, whether or not it succeeds, whether or not there's
+     an error::
+
+	void complete_request_key(struct key_construction *cons, int error);
+
+     The error parameter should be 0 on success, -ve on error.  The
+     construction record is destroyed by this action and the authorisation key
+     will be revoked.  If an error is indicated, the key under construction
+     will be negatively instantiated if it wasn't already instantiated.
+
+     If this method returns an error, that error will be returned to the
+     caller of request_key*().  complete_request_key() must be called prior to
+     returning.
+
+     The key under construction and the authorisation key can be found in the
+     key_construction struct pointed to by cons:
+
+      *  ``struct key *key;``
+
+     	 The key under construction.
+
+      *  ``struct key *authkey;``
+
+     	 The authorisation key.
+
+
+  *  ``struct key_restriction *(*lookup_restriction)(const char *params);``
+
+     This optional method is used to enable userspace configuration of keyring
+     restrictions. The restriction parameter string (not including the key type
+     name) is passed in, and this method returns a pointer to a key_restriction
+     structure containing the relevant functions and data to evaluate each
+     attempted key link operation. If there is no match, -EINVAL is returned.
+
+
+  *  ``asym_eds_op`` and ``asym_verify_signature``::
+
+       int (*asym_eds_op)(struct kernel_pkey_params *params,
+			  const void *in, void *out);
+       int (*asym_verify_signature)(struct kernel_pkey_params *params,
+				    const void *in, const void *in2);
+
+     These methods are optional.  If provided the first allows a key to be
+     used to encrypt, decrypt or sign a blob of data, and the second allows a
+     key to verify a signature.
+
+     In all cases, the following information is provided in the params block::
+
+	struct kernel_pkey_params {
+		struct key	*key;
+		const char	*encoding;
+		const char	*hash_algo;
+		char		*info;
+		__u32		in_len;
+		union {
+			__u32	out_len;
+			__u32	in2_len;
+		};
+		enum kernel_pkey_operation op : 8;
+	};
+
+     This includes the key to be used; a string indicating the encoding to use
+     (for instance, "pkcs1" may be used with an RSA key to indicate
+     RSASSA-PKCS1-v1.5 or RSAES-PKCS1-v1.5 encoding or "raw" if no encoding);
+     the name of the hash algorithm used to generate the data for a signature
+     (if appropriate); the sizes of the input and output (or second input)
+     buffers; and the ID of the operation to be performed.
+
+     For a given operation ID, the input and output buffers are used as
+     follows::
+
+	Operation ID		in,in_len	out,out_len	in2,in2_len
+	=======================	===============	===============	===============
+	kernel_pkey_encrypt	Raw data	Encrypted data	-
+	kernel_pkey_decrypt	Encrypted data	Raw data	-
+	kernel_pkey_sign	Raw data	Signature	-
+	kernel_pkey_verify	Raw data	-		Signature
+
+     asym_eds_op() deals with encryption, decryption and signature creation as
+     specified by params->op.  Note that params->op is also set for
+     asym_verify_signature().
+
+     Encrypting and signature creation both take raw data in the input buffer
+     and return the encrypted result in the output buffer.  Padding may have
+     been added if an encoding was set.  In the case of signature creation,
+     depending on the encoding, the padding created may need to indicate the
+     digest algorithm - the name of which should be supplied in hash_algo.
+
+     Decryption takes encrypted data in the input buffer and returns the raw
+     data in the output buffer.  Padding will get checked and stripped off if
+     an encoding was set.
+
+     Verification takes raw data in the input buffer and the signature in the
+     second input buffer and checks that the one matches the other.  Padding
+     will be validated.  Depending on the encoding, the digest algorithm used
+     to generate the raw data may need to be indicated in hash_algo.
+
+     If successful, asym_eds_op() should return the number of bytes written
+     into the output buffer.  asym_verify_signature() should return 0.
+
+     A variety of errors may be returned, including EOPNOTSUPP if the operation
+     is not supported; EKEYREJECTED if verification fails; ENOPKG if the
+     required crypto isn't available.
+
+
+  *  ``asym_query``::
+
+       int (*asym_query)(const struct kernel_pkey_params *params,
+			 struct kernel_pkey_query *info);
+
+     This method is optional.  If provided it allows information about the
+     public or asymmetric key held in the key to be determined.
+
+     The parameter block is as for asym_eds_op() and co. but in_len and out_len
+     are unused.  The encoding and hash_algo fields should be used to reduce
+     the returned buffer/data sizes as appropriate.
+
+     If successful, the following information is filled in::
+
+	struct kernel_pkey_query {
+		__u32		supported_ops;
+		__u32		key_size;
+		__u16		max_data_size;
+		__u16		max_sig_size;
+		__u16		max_enc_size;
+		__u16		max_dec_size;
+	};
+
+     The supported_ops field will contain a bitmask indicating what operations
+     are supported by the key, including encryption of a blob, decryption of a
+     blob, signing a blob and verifying the signature on a blob.  The following
+     constants are defined for this::
+
+	KEYCTL_SUPPORTS_{ENCRYPT,DECRYPT,SIGN,VERIFY}
+
+     The key_size field is the size of the key in bits.  max_data_size and
+     max_sig_size are the maximum raw data and signature sizes for creation and
+     verification of a signature; max_enc_size and max_dec_size are the maximum
+     raw data and signature sizes for encryption and decryption.  The
+     max_*_size fields are measured in bytes.
+
+     If successful, 0 will be returned.  If the key doesn't support this,
+     EOPNOTSUPP will be returned.
+
+
+Request-Key Callback Service
+============================
+
+To create a new key, the kernel will attempt to execute the following command
+line::
+
+	/sbin/request-key create <key> <uid> <gid> \
+		<threadring> <processring> <sessionring> <callout_info>
+
+<key> is the key being constructed, and the three keyrings are the process
+keyrings from the process that caused the search to be issued. These are
+included for two reasons:
+
+   1  There may be an authentication token in one of the keyrings that is
+      required to obtain the key, eg: a Kerberos Ticket-Granting Ticket.
+
+   2  The new key should probably be cached in one of these rings.
+
+This program should set it UID and GID to those specified before attempting to
+access any more keys. It may then look around for a user specific process to
+hand the request off to (perhaps a path held in placed in another key by, for
+example, the KDE desktop manager).
+
+The program (or whatever it calls) should finish construction of the key by
+calling KEYCTL_INSTANTIATE or KEYCTL_INSTANTIATE_IOV, which also permits it to
+cache the key in one of the keyrings (probably the session ring) before
+returning.  Alternatively, the key can be marked as negative with KEYCTL_NEGATE
+or KEYCTL_REJECT; this also permits the key to be cached in one of the
+keyrings.
+
+If it returns with the key remaining in the unconstructed state, the key will
+be marked as being negative, it will be added to the session keyring, and an
+error will be returned to the key requestor.
+
+Supplementary information may be provided from whoever or whatever invoked this
+service. This will be passed as the <callout_info> parameter. If no such
+information was made available, then "-" will be passed as this parameter
+instead.
+
+
+Similarly, the kernel may attempt to update an expired or a soon to expire key
+by executing::
+
+	/sbin/request-key update <key> <uid> <gid> \
+		<threadring> <processring> <sessionring>
+
+In this case, the program isn't required to actually attach the key to a ring;
+the rings are provided for reference.
+
+
+Garbage Collection
+==================
+
+Dead keys (for which the type has been removed) will be automatically unlinked
+from those keyrings that point to them and deleted as soon as possible by a
+background garbage collector.
+
+Similarly, revoked and expired keys will be garbage collected, but only after a
+certain amount of time has passed.  This time is set as a number of seconds in::
+
+	/proc/sys/kernel/keys/gc_delay
diff --git a/Documentation/security/keys/ecryptfs.rst b/Documentation/security/keys/ecryptfs.rst
new file mode 100644
index 000000000..0e2be0a6b
--- /dev/null
+++ b/Documentation/security/keys/ecryptfs.rst
@@ -0,0 +1,73 @@
+==========================================
+Encrypted keys for the eCryptfs filesystem
+==========================================
+
+ECryptfs is a stacked filesystem which transparently encrypts and decrypts each
+file using a randomly generated File Encryption Key (FEK).
+
+Each FEK is in turn encrypted with a File Encryption Key Encryption Key (FEKEK)
+either in kernel space or in user space with a daemon called 'ecryptfsd'.  In
+the former case the operation is performed directly by the kernel CryptoAPI
+using a key, the FEKEK, derived from a user prompted passphrase;  in the latter
+the FEK is encrypted by 'ecryptfsd' with the help of external libraries in order
+to support other mechanisms like public key cryptography, PKCS#11 and TPM based
+operations.
+
+The data structure defined by eCryptfs to contain information required for the
+FEK decryption is called authentication token and, currently, can be stored in a
+kernel key of the 'user' type, inserted in the user's session specific keyring
+by the userspace utility 'mount.ecryptfs' shipped with the package
+'ecryptfs-utils'.
+
+The 'encrypted' key type has been extended with the introduction of the new
+format 'ecryptfs' in order to be used in conjunction with the eCryptfs
+filesystem.  Encrypted keys of the newly introduced format store an
+authentication token in its payload with a FEKEK randomly generated by the
+kernel and protected by the parent master key.
+
+In order to avoid known-plaintext attacks, the datablob obtained through
+commands 'keyctl print' or 'keyctl pipe' does not contain the overall
+authentication token, which content is well known, but only the FEKEK in
+encrypted form.
+
+The eCryptfs filesystem may really benefit from using encrypted keys in that the
+required key can be securely generated by an Administrator and provided at boot
+time after the unsealing of a 'trusted' key in order to perform the mount in a
+controlled environment.  Another advantage is that the key is not exposed to
+threats of malicious software, because it is available in clear form only at
+kernel level.
+
+Usage::
+
+   keyctl add encrypted name "new ecryptfs key-type:master-key-name keylen" ring
+   keyctl add encrypted name "load hex_blob" ring
+   keyctl update keyid "update key-type:master-key-name"
+
+Where::
+
+	name:= '<16 hexadecimal characters>'
+	key-type:= 'trusted' | 'user'
+	keylen:= 64
+
+
+Example of encrypted key usage with the eCryptfs filesystem:
+
+Create an encrypted key "1000100010001000" of length 64 bytes with format
+'ecryptfs' and save it using a previously loaded user key "test"::
+
+    $ keyctl add encrypted 1000100010001000 "new ecryptfs user:test 64" @u
+    19184530
+
+    $ keyctl print 19184530
+    ecryptfs user:test 64 490045d4bfe48c99f0d465fbbbb79e7500da954178e2de0697
+    dd85091f5450a0511219e9f7cd70dcd498038181466f78ac8d4c19504fcc72402bfc41c2
+    f253a41b7507ccaa4b2b03fff19a69d1cc0b16e71746473f023a95488b6edfd86f7fdd40
+    9d292e4bacded1258880122dd553a661
+
+    $ keyctl pipe 19184530 > ecryptfs.blob
+
+Mount an eCryptfs filesystem using the created encrypted key "1000100010001000"
+into the '/secret' directory::
+
+    $ mount -i -t ecryptfs -oecryptfs_sig=1000100010001000,\
+      ecryptfs_cipher=aes,ecryptfs_key_bytes=32 /secret /secret
diff --git a/Documentation/security/keys/index.rst b/Documentation/security/keys/index.rst
new file mode 100644
index 000000000..647d58f25
--- /dev/null
+++ b/Documentation/security/keys/index.rst
@@ -0,0 +1,11 @@
+===========
+Kernel Keys
+===========
+
+.. toctree::
+   :maxdepth: 1
+
+   core
+   ecryptfs
+   request-key
+   trusted-encrypted
diff --git a/Documentation/security/keys/request-key.rst b/Documentation/security/keys/request-key.rst
new file mode 100644
index 000000000..35f2296b7
--- /dev/null
+++ b/Documentation/security/keys/request-key.rst
@@ -0,0 +1,207 @@
+===================
+Key Request Service
+===================
+
+The key request service is part of the key retention service (refer to
+Documentation/security/keys/core.rst).  This document explains more fully how
+the requesting algorithm works.
+
+The process starts by either the kernel requesting a service by calling
+``request_key*()``::
+
+	struct key *request_key(const struct key_type *type,
+				const char *description,
+				const char *callout_info);
+
+or::
+
+	struct key *request_key_tag(const struct key_type *type,
+				    const char *description,
+				    const struct key_tag *domain_tag,
+				    const char *callout_info);
+
+or::
+
+	struct key *request_key_with_auxdata(const struct key_type *type,
+					     const char *description,
+					     const struct key_tag *domain_tag,
+					     const char *callout_info,
+					     size_t callout_len,
+					     void *aux);
+
+or::
+
+	struct key *request_key_rcu(const struct key_type *type,
+				    const char *description,
+				    const struct key_tag *domain_tag);
+
+Or by userspace invoking the request_key system call::
+
+	key_serial_t request_key(const char *type,
+				 const char *description,
+				 const char *callout_info,
+				 key_serial_t dest_keyring);
+
+The main difference between the access points is that the in-kernel interface
+does not need to link the key to a keyring to prevent it from being immediately
+destroyed.  The kernel interface returns a pointer directly to the key, and
+it's up to the caller to destroy the key.
+
+The request_key_tag() call is like the in-kernel request_key(), except that it
+also takes a domain tag that allows keys to be separated by namespace and
+killed off as a group.
+
+The request_key_with_auxdata() calls is like the request_key_tag() call, except
+that they permit auxiliary data to be passed to the upcaller (the default is
+NULL).  This is only useful for those key types that define their own upcall
+mechanism rather than using /sbin/request-key.
+
+The request_key_rcu() call is like the request_key_tag() call, except that it
+doesn't check for keys that are under construction and doesn't attempt to
+construct missing keys.
+
+The userspace interface links the key to a keyring associated with the process
+to prevent the key from going away, and returns the serial number of the key to
+the caller.
+
+
+The following example assumes that the key types involved don't define their
+own upcall mechanisms.  If they do, then those should be substituted for the
+forking and execution of /sbin/request-key.
+
+
+The Process
+===========
+
+A request proceeds in the following manner:
+
+  1) Process A calls request_key() [the userspace syscall calls the kernel
+     interface].
+
+  2) request_key() searches the process's subscribed keyrings to see if there's
+     a suitable key there.  If there is, it returns the key.  If there isn't,
+     and callout_info is not set, an error is returned.  Otherwise the process
+     proceeds to the next step.
+
+  3) request_key() sees that A doesn't have the desired key yet, so it creates
+     two things:
+
+      a) An uninstantiated key U of requested type and description.
+
+      b) An authorisation key V that refers to key U and notes that process A
+     	 is the context in which key U should be instantiated and secured, and
+     	 from which associated key requests may be satisfied.
+
+  4) request_key() then forks and executes /sbin/request-key with a new session
+     keyring that contains a link to auth key V.
+
+  5) /sbin/request-key assumes the authority associated with key U.
+
+  6) /sbin/request-key execs an appropriate program to perform the actual
+     instantiation.
+
+  7) The program may want to access another key from A's context (say a
+     Kerberos TGT key).  It just requests the appropriate key, and the keyring
+     search notes that the session keyring has auth key V in its bottom level.
+
+     This will permit it to then search the keyrings of process A with the
+     UID, GID, groups and security info of process A as if it was process A,
+     and come up with key W.
+
+  8) The program then does what it must to get the data with which to
+     instantiate key U, using key W as a reference (perhaps it contacts a
+     Kerberos server using the TGT) and then instantiates key U.
+
+  9) Upon instantiating key U, auth key V is automatically revoked so that it
+     may not be used again.
+
+  10) The program then exits 0 and request_key() deletes key V and returns key
+      U to the caller.
+
+This also extends further.  If key W (step 7 above) didn't exist, key W would
+be created uninstantiated, another auth key (X) would be created (as per step
+3) and another copy of /sbin/request-key spawned (as per step 4); but the
+context specified by auth key X will still be process A, as it was in auth key
+V.
+
+This is because process A's keyrings can't simply be attached to
+/sbin/request-key at the appropriate places because (a) execve will discard two
+of them, and (b) it requires the same UID/GID/Groups all the way through.
+
+
+Negative Instantiation And Rejection
+====================================
+
+Rather than instantiating a key, it is possible for the possessor of an
+authorisation key to negatively instantiate a key that's under construction.
+This is a short duration placeholder that causes any attempt at re-requesting
+the key while it exists to fail with error ENOKEY if negated or the specified
+error if rejected.
+
+This is provided to prevent excessive repeated spawning of /sbin/request-key
+processes for a key that will never be obtainable.
+
+Should the /sbin/request-key process exit anything other than 0 or die on a
+signal, the key under construction will be automatically negatively
+instantiated for a short amount of time.
+
+
+The Search Algorithm
+====================
+
+A search of any particular keyring proceeds in the following fashion:
+
+  1) When the key management code searches for a key (keyring_search_rcu) it
+     firstly calls key_permission(SEARCH) on the keyring it's starting with,
+     if this denies permission, it doesn't search further.
+
+  2) It considers all the non-keyring keys within that keyring and, if any key
+     matches the criteria specified, calls key_permission(SEARCH) on it to see
+     if the key is allowed to be found.  If it is, that key is returned; if
+     not, the search continues, and the error code is retained if of higher
+     priority than the one currently set.
+
+  3) It then considers all the keyring-type keys in the keyring it's currently
+     searching.  It calls key_permission(SEARCH) on each keyring, and if this
+     grants permission, it recurses, executing steps (2) and (3) on that
+     keyring.
+
+The process stops immediately a valid key is found with permission granted to
+use it.  Any error from a previous match attempt is discarded and the key is
+returned.
+
+When request_key() is invoked, if CONFIG_KEYS_REQUEST_CACHE=y, a per-task
+one-key cache is first checked for a match.
+
+When search_process_keyrings() is invoked, it performs the following searches
+until one succeeds:
+
+  1) If extant, the process's thread keyring is searched.
+
+  2) If extant, the process's process keyring is searched.
+
+  3) The process's session keyring is searched.
+
+  4) If the process has assumed the authority associated with a request_key()
+     authorisation key then:
+
+      a) If extant, the calling process's thread keyring is searched.
+
+      b) If extant, the calling process's process keyring is searched.
+
+      c) The calling process's session keyring is searched.
+
+The moment one succeeds, all pending errors are discarded and the found key is
+returned.  If CONFIG_KEYS_REQUEST_CACHE=y, then that key is placed in the
+per-task cache, displacing the previous key.  The cache is cleared on exit or
+just prior to resumption of userspace.
+
+Only if all these fail does the whole thing fail with the highest priority
+error.  Note that several errors may have come from LSM.
+
+The error priority is::
+
+	EKEYREVOKED > EKEYEXPIRED > ENOKEY
+
+EACCES/EPERM are only returned on a direct search of a specific keyring where
+the basal keyring does not grant Search permission.
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
new file mode 100644
index 000000000..ddff7c7c2
--- /dev/null
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -0,0 +1,617 @@
+==========================
+Trusted and Encrypted Keys
+==========================
+
+Trusted and Encrypted Keys are two new key types added to the existing kernel
+key ring service.  Both of these new types are variable length symmetric keys,
+and in both cases all keys are created in the kernel, and user space sees,
+stores, and loads only encrypted blobs.  Trusted Keys require the availability
+of a Trust Source for greater security, while Encrypted Keys can be used on any
+system. All user level blobs, are displayed and loaded in hex ASCII for
+convenience, and are integrity verified.
+
+Trusted Keys as Protected key
+=============================
+It is the secure way of keeping the keys in the kernel key-ring as Trusted-Key,
+such that:
+
+- Key-blob, an encrypted key-data, created to be stored, loaded and seen by
+  userspace.
+- Key-data, the plain-key text in the system memory, to be used by
+  kernel space only.
+
+Though key-data is not accessible to the user-space in plain-text, but it is in
+plain-text in system memory, when used in kernel space. Even though kernel-space
+attracts small surface attack, but with compromised kernel or side-channel
+attack accessing the system memory can lead to a chance of the key getting
+compromised/leaked.
+
+In order to protect the key in kernel space, the concept of "protected-keys" is
+introduced which will act as an added layer of protection. The key-data of the
+protected keys is encrypted with Key-Encryption-Key(KEK), and decrypted inside
+the trust source boundary. The plain-key text never available out-side in the
+system memory. Thus, any crypto operation that is to be executed using the
+protected key, can only be done by the trust source, which generated the
+key blob.
+
+Hence, if the protected-key is leaked or compromised, it is of no use to the
+hacker.
+
+Trusted keys as protected keys, with trust source having the capability of
+generating:
+
+- Key-Blob, to be loaded, stored and seen by user-space.
+
+Trust Source
+============
+
+A trust source provides the source of security for Trusted Keys.  This
+section lists currently supported trust sources, along with their security
+considerations.  Whether or not a trust source is sufficiently safe depends
+on the strength and correctness of its implementation, as well as the threat
+environment for a specific use case.  Since the kernel doesn't know what the
+environment is, and there is no metric of trust, it is dependent on the
+consumer of the Trusted Keys to determine if the trust source is sufficiently
+safe.
+
+  *  Root of trust for storage
+
+     (1) TPM (Trusted Platform Module: hardware device)
+
+         Rooted to Storage Root Key (SRK) which never leaves the TPM that
+         provides crypto operation to establish root of trust for storage.
+
+     (2) TEE (Trusted Execution Environment: OP-TEE based on Arm TrustZone)
+
+         Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip
+         fuses and is accessible to TEE only.
+
+     (3) CAAM (Cryptographic Acceleration and Assurance Module: IP on NXP SoCs)
+
+         When High Assurance Boot (HAB) is enabled and the CAAM is in secure
+         mode, trust is rooted to the OTPMK, a never-disclosed 256-bit key
+         randomly generated and fused into each SoC at manufacturing time.
+         Otherwise, a common fixed test key is used instead.
+
+     (4) DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
+
+         Rooted to a one-time programmable key (OTP) that is generally burnt
+         in the on-chip fuses and is accessible to the DCP encryption engine only.
+         DCP provides two keys that can be used as root of trust: the OTP key
+         and the UNIQUE key. Default is to use the UNIQUE key, but selecting
+         the OTP key can be done via a module parameter (dcp_use_otp_key).
+
+     (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore)
+
+         Rooted to a unique, per-LPAR key, which is derived from a system-wide,
+         randomly generated LPAR root key. Both the per-LPAR keys and the LPAR
+         root key are stored in hypervisor-owned secure memory at runtime,
+         and the LPAR root key is additionally persisted in secure locations
+         such as the processor SEEPROMs and encrypted NVRAM.
+
+  *  Execution isolation
+
+     (1) TPM
+
+         Fixed set of operations running in isolated execution environment.
+
+     (2) TEE
+
+         Customizable set of operations running in isolated execution
+         environment verified via Secure/Trusted boot process.
+
+     (3) CAAM
+
+         Fixed set of operations running in isolated execution environment.
+
+     (4) DCP
+
+         Fixed set of cryptographic operations running in isolated execution
+         environment. Only basic blob key encryption is executed there.
+         The actual key sealing/unsealing is done on main processor/kernel space.
+
+     (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore)
+
+         Fixed set of cryptographic operations done on on-chip hardware
+         cryptographic acceleration unit NX. Keys for wrapping and unwrapping
+         are managed by PowerVM Platform KeyStore, which stores keys in an
+         isolated in-memory copy in secure hypervisor memory, as well as in a
+         persistent copy in hypervisor-encrypted NVRAM.
+
+  * Optional binding to platform integrity state
+
+     (1) TPM
+
+         Keys can be optionally sealed to specified PCR (integrity measurement)
+         values, and only unsealed by the TPM, if PCRs and blob integrity
+         verifications match. A loaded Trusted Key can be updated with new
+         (future) PCR values, so keys are easily migrated to new PCR values,
+         such as when the kernel and initramfs are updated. The same key can
+         have many saved blobs under different PCR values, so multiple boots are
+         easily supported.
+
+     (2) TEE
+
+         Relies on Secure/Trusted boot process for platform integrity. It can
+         be extended with TEE based measured boot process.
+
+     (3) CAAM
+
+         Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs
+         for platform integrity.
+
+     (4) DCP
+
+         Relies on Secure/Trusted boot process (called HAB by vendor) for
+         platform integrity.
+
+     (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore)
+
+         Relies on secure and trusted boot process of IBM Power systems for
+         platform integrity.
+
+  *  Interfaces and APIs
+
+     (1) TPM
+
+         TPMs have well-documented, standardized interfaces and APIs.
+
+     (2) TEE
+
+         TEEs have well-documented, standardized client interface and APIs. For
+         more details refer to ``Documentation/driver-api/tee.rst``.
+
+     (3) CAAM
+
+         Interface is specific to silicon vendor.
+
+     (4) DCP
+
+         Vendor-specific API that is implemented as part of the DCP crypto driver in
+         ``drivers/crypto/mxs-dcp.c``.
+
+     (5) PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore)
+
+         Platform Keystore has well documented interfaces in PAPR document.
+         Refer to ``Documentation/arch/powerpc/papr_hcalls.rst``
+
+  *  Threat model
+
+     The strength and appropriateness of a particular trust source for a given
+     purpose must be assessed when using them to protect security-relevant data.
+
+
+Key Generation
+==============
+
+Trusted Keys
+------------
+
+New keys are created from random numbers. They are encrypted/decrypted using
+a child key in the storage key hierarchy. Encryption and decryption of the
+child key must be protected by a strong access control policy within the
+trust source. The random number generator in use differs according to the
+selected trust source:
+
+  *  TPM: hardware device based RNG
+
+     Keys are generated within the TPM. Strength of random numbers may vary
+     from one device manufacturer to another.
+
+  *  TEE: OP-TEE based on Arm TrustZone based RNG
+
+     RNG is customizable as per platform needs. It can either be direct output
+     from platform specific hardware RNG or a software based Fortuna CSPRNG
+     which can be seeded via multiple entropy sources.
+
+  *  CAAM: Kernel RNG
+
+     The normal kernel random number generator is used. To seed it from the
+     CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device
+     is probed.
+
+  *  DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
+
+     The DCP hardware device itself does not provide a dedicated RNG interface,
+     so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do have
+     a dedicated hardware RNG that is independent from DCP which can be enabled
+     to back the kernel RNG.
+
+   * PKWM (PowerVM Key Wrapping Module: IBM PowerVM + Platform KeyStore)
+
+     The normal kernel random number generator is used to generate keys.
+
+Users may override this by specifying ``trusted.rng=kernel`` on the kernel
+command-line to override the used RNG with the kernel's random number pool.
+
+Encrypted Keys
+--------------
+
+Encrypted keys do not depend on a trust source, and are faster, as they use AES
+for encryption/decryption. New keys are created either from kernel-generated
+random numbers or user-provided decrypted data, and are encrypted/decrypted
+using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or
+user-key type. The main disadvantage of encrypted keys is that if they are not
+rooted in a trusted key, they are only as secure as the user key encrypting
+them. The master user key should therefore be loaded in as secure a way as
+possible, preferably early in boot.
+
+
+Usage
+=====
+
+Trusted Keys usage: TPM
+-----------------------
+
+TPM 1.2: By default, trusted keys are sealed under the SRK, which has the
+default authorization value (20 bytes of 0s).  This can be set at takeownership
+time with the TrouSerS utility: "tpm_takeownership -u -z".
+
+TPM 2.0: The user must first create a storage key and make it persistent, so the
+key is available after reboot. This can be done using the following commands.
+
+With the IBM TSS 2 stack::
+
+  #> tsscreateprimary -hi o -st
+  Handle 80000000
+  #> tssevictcontrol -hi o -ho 80000000 -hp 81000001
+
+Or with the Intel TSS 2 stack::
+
+  #> tpm2_createprimary --hierarchy o -G rsa2048 -c key.ctxt
+  [...]
+  #> tpm2_evictcontrol -c key.ctxt 0x81000001
+  persistentHandle: 0x81000001
+
+Usage::
+
+    keyctl add trusted name "new keylen [options]" ring
+    keyctl add trusted name "load hex_blob [pcrlock=pcrnum]" ring
+    keyctl update key "update [options]"
+    keyctl print keyid
+
+    options:
+       keyhandle=    ascii hex value of sealing key
+                       TPM 1.2: default 0x40000000 (SRK)
+                       TPM 2.0: no default; must be passed every time
+       keyauth=	     ascii hex auth for sealing key default 0x00...i
+                     (40 ascii zeros)
+       blobauth=     ascii hex auth for sealed data default 0x00...
+                     (40 ascii zeros)
+       pcrinfo=	     ascii hex of PCR_INFO or PCR_INFO_LONG (no default)
+       pcrlock=	     pcr number to be extended to "lock" blob
+       migratable=   0|1 indicating permission to reseal to new PCR values,
+                     default 1 (resealing allowed)
+       hash=         hash algorithm name as a string. For TPM 1.x the only
+                     allowed value is sha1. For TPM 2.x the allowed values
+                     are sha1, sha256, sha384, sha512 and sm3-256.
+       policydigest= digest for the authorization policy. must be calculated
+                     with the same hash algorithm as specified by the 'hash='
+                     option.
+       policyhandle= handle to an authorization policy session that defines the
+                     same policy and with the same hash algorithm as was used to
+                     seal the key.
+
+"keyctl print" returns an ascii hex copy of the sealed key, which is in standard
+TPM_STORED_DATA format.  The key length for new keys are always in bytes.
+Trusted Keys can be 32 - 128 bytes (256 - 1024 bits), the upper limit is to fit
+within the 2048 bit SRK (RSA) keylength, with all necessary structure/padding.
+
+Trusted Keys usage: TEE
+-----------------------
+
+Usage::
+
+    keyctl add trusted name "new keylen" ring
+    keyctl add trusted name "load hex_blob" ring
+    keyctl print keyid
+
+"keyctl print" returns an ASCII hex copy of the sealed key, which is in format
+specific to TEE device implementation.  The key length for new keys is always
+in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
+Trusted Keys usage: CAAM
+------------------------
+
+Trusted Keys Usage::
+
+    keyctl add trusted name "new keylen" ring
+    keyctl add trusted name "load hex_blob" ring
+    keyctl print keyid
+
+"keyctl print" returns an ASCII hex copy of the sealed key, which is in a
+CAAM-specific format.  The key length for new keys is always in bytes.
+Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
+Trusted Keys as Protected Keys Usage::
+
+    keyctl add trusted name "new keylen pk [options]" ring
+    keyctl add trusted name "load hex_blob [options]" ring
+    keyctl print keyid
+
+    where, 'pk' is used to direct trust source to generate protected key.
+
+    options:
+       key_enc_algo =      For CAAM, supported enc algo are ECB(2), CCM(1).
+
+"keyctl print" returns an ASCII hex copy of the sealed key, which is in a
+CAAM-specific format.  The key length for new keys is always in bytes.
+Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
+Trusted Keys usage: DCP
+-----------------------
+
+Usage::
+
+    keyctl add trusted name "new keylen" ring
+    keyctl add trusted name "load hex_blob" ring
+    keyctl print keyid
+
+"keyctl print" returns an ASCII hex copy of the sealed key, which is in format
+specific to this DCP key-blob implementation.  The key length for new keys is
+always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
+Trusted Keys usage: PKWM
+------------------------
+
+Usage::
+
+    keyctl add trusted name "new keylen [options]" ring
+    keyctl add trusted name "load hex_blob" ring
+    keyctl print keyid
+
+    options:
+       wrap_flags=   ascii hex value of security policy requirement
+                       0x00: no secure boot requirement (default)
+                       0x01: require secure boot to be in either audit or
+                             enforced mode
+                       0x02: require secure boot to be in enforced mode
+
+"keyctl print" returns an ASCII hex copy of the sealed key, which is in format
+specific to PKWM key-blob implementation.  The key length for new keys is
+always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
+Encrypted Keys usage
+--------------------
+
+The decrypted portion of encrypted keys can contain either a simple symmetric
+key or a more complex structure. The format of the more complex structure is
+application specific, which is identified by 'format'.
+
+Usage::
+
+    keyctl add encrypted name "new [format] key-type:master-key-name keylen"
+        ring
+    keyctl add encrypted name "new [format] key-type:master-key-name keylen
+        decrypted-data" ring
+    keyctl add encrypted name "load hex_blob" ring
+    keyctl update keyid "update key-type:master-key-name"
+
+Where::
+
+	format:= 'default | ecryptfs | enc32'
+	key-type:= 'trusted' | 'user'
+
+Examples of trusted and encrypted key usage
+-------------------------------------------
+
+Create and save a trusted key named "kmk" of length 32 bytes.
+
+Note: When using a TPM 2.0 with a persistent key with handle 0x81000001,
+append 'keyhandle=0x81000001' to statements between quotes, such as
+"new 32 keyhandle=0x81000001".
+
+::
+
+    $ keyctl add trusted kmk "new 32" @u
+    440502848
+
+    $ keyctl show
+    Session Keyring
+           -3 --alswrv    500   500  keyring: _ses
+     97833714 --alswrv    500    -1   \_ keyring: _uid.500
+    440502848 --alswrv    500   500       \_ trusted: kmk
+
+    $ keyctl print 440502848
+    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
+    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
+    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
+    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
+    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
+    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
+    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
+    e4a8aea2b607ec96931e6f4d4fe563ba
+
+    $ keyctl pipe 440502848 > kmk.blob
+
+Load a trusted key from the saved blob::
+
+    $ keyctl add trusted kmk "load `cat kmk.blob`" @u
+    268728824
+
+    $ keyctl print 268728824
+    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
+    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
+    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
+    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
+    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
+    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
+    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
+    e4a8aea2b607ec96931e6f4d4fe563ba
+
+Create and save a trusted key as protected key named "kmk" of length 32 bytes.
+
+::
+
+    $ keyctl add trusted kmk "new 32 pk key_enc_algo=1" @u
+    440502848
+
+    $ keyctl show
+    Session Keyring
+           -3 --alswrv    500   500  keyring: _ses
+     97833714 --alswrv    500    -1   \_ keyring: _uid.500
+    440502848 --alswrv    500   500       \_ trusted: kmk
+
+    $ keyctl print 440502848
+    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
+    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
+    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
+    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
+    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
+    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
+    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
+    e4a8aea2b607ec96931e6f4d4fe563ba
+
+    $ keyctl pipe 440502848 > kmk.blob
+
+Load a trusted key from the saved blob::
+
+    $ keyctl add trusted kmk "load `cat kmk.blob` key_enc_algo=1" @u
+    268728824
+
+    $ keyctl print 268728824
+    0101000000000000000001005d01b7e3f4a6be5709930f3b70a743cbb42e0cc95e18e915
+    3f60da455bbf1144ad12e4f92b452f966929f6105fd29ca28e4d4d5a031d068478bacb0b
+    27351119f822911b0a11ba3d3498ba6a32e50dac7f32894dd890eb9ad578e4e292c83722
+    a52e56a097e6a68b3f56f7a52ece0cdccba1eb62cad7d817f6dc58898b3ac15f36026fec
+    d568bd4a706cb60bb37be6d8f1240661199d640b66fb0fe3b079f97f450b9ef9c22c6d5d
+    dd379f0facd1cd020281dfa3c70ba21a3fa6fc2471dc6d13ecf8298b946f65345faa5ef0
+    f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b
+    e4a8aea2b607ec96931e6f4d4fe563ba
+
+Reseal (TPM specific) a trusted key under new PCR values::
+
+    $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
+    $ keyctl print 268728824
+    010100000000002c0002800093c35a09b70fff26e7a98ae786c641e678ec6ffb6b46d805
+    77c8a6377aed9d3219c6dfec4b23ffe3000001005d37d472ac8a44023fbb3d18583a4f73
+    d3a076c0858f6f1dcaa39ea0f119911ff03f5406df4f7f27f41da8d7194f45c9f4e00f2e
+    df449f266253aa3f52e55c53de147773e00f0f9aca86c64d94c95382265968c354c5eab4
+    9638c5ae99c89de1e0997242edfb0b501744e11ff9762dfd951cffd93227cc513384e7e6
+    e782c29435c7ec2edafaa2f4c1fe6e7a781b59549ff5296371b42133777dcc5b8b971610
+    94bc67ede19e43ddb9dc2baacad374a36feaf0314d700af0a65c164b7082401740e489c9
+    7ef6a24defe4846104209bf0c3eced7fa1a672ed5b125fc9d8cd88b476a658a4434644ef
+    df8ae9a178e9f83ba9f08d10fa47e4226b98b0702f06b3b8
+
+
+The initial consumer of trusted keys is EVM, which at boot time needs a high
+quality symmetric key for HMAC protection of file metadata. The use of a
+trusted key provides strong guarantees that the EVM key has not been
+compromised by a user level problem, and when sealed to a platform integrity
+state, protects against boot and offline attacks. Create and save an
+encrypted key "evm" using the above trusted key "kmk":
+
+option 1: omitting 'format'::
+
+    $ keyctl add encrypted evm "new trusted:kmk 32" @u
+    159771175
+
+option 2: explicitly defining 'format' as 'default'::
+
+    $ keyctl add encrypted evm "new default trusted:kmk 32" @u
+    159771175
+
+    $ keyctl print 159771175
+    default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
+    82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
+    24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
+
+    $ keyctl pipe 159771175 > evm.blob
+
+Load an encrypted key "evm" from saved blob::
+
+    $ keyctl add encrypted evm "load `cat evm.blob`" @u
+    831684262
+
+    $ keyctl print 831684262
+    default trusted:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b3
+    82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
+    24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
+
+Instantiate an encrypted key "evm" using user-provided decrypted data::
+
+    $ evmkey=$(dd if=/dev/urandom bs=1 count=32 | xxd -c32 -p)
+    $ keyctl add encrypted evm "new default user:kmk 32 $evmkey" @u
+    794890253
+
+    $ keyctl print 794890253
+    default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d
+    bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247
+    17c64 5972dcb82ab2dde83376d82b2e3c09ffc
+
+Other uses for trusted and encrypted keys, such as for disk and file encryption
+are anticipated.  In particular the new format 'ecryptfs' has been defined
+in order to use encrypted keys to mount an eCryptfs filesystem.  More details
+about the usage can be found in the file
+``Documentation/security/keys/ecryptfs.rst``.
+
+Another new format 'enc32' has been defined in order to support encrypted keys
+with payload size of 32 bytes. This will initially be used for nvdimm security
+but may expand to other usages that require 32 bytes payload.
+
+
+TPM 2.0 ASN.1 Key Format
+------------------------
+
+The TPM 2.0 ASN.1 key format is designed to be easily recognisable,
+even in binary form (fixing a problem we had with the TPM 1.2 ASN.1
+format) and to be extensible for additions like importable keys and
+policy::
+
+    TPMKey ::= SEQUENCE {
+        type		OBJECT IDENTIFIER
+        emptyAuth	[0] EXPLICIT BOOLEAN OPTIONAL
+        parent		INTEGER
+        pubkey		OCTET STRING
+        privkey		OCTET STRING
+    }
+
+type is what distinguishes the key even in binary form since the OID
+is provided by the TCG to be unique and thus forms a recognizable
+binary pattern at offset 3 in the key.  The OIDs currently made
+available are::
+
+    2.23.133.10.1.3 TPM Loadable key.  This is an asymmetric key (Usually
+                    RSA2048 or Elliptic Curve) which can be imported by a
+                    TPM2_Load() operation.
+
+    2.23.133.10.1.4 TPM Importable Key.  This is an asymmetric key (Usually
+                    RSA2048 or Elliptic Curve) which can be imported by a
+                    TPM2_Import() operation.
+
+    2.23.133.10.1.5 TPM Sealed Data.  This is a set of data (up to 128
+                    bytes) which is sealed by the TPM.  It usually
+                    represents a symmetric key and must be unsealed before
+                    use.
+
+The trusted key code only uses the TPM Sealed Data OID.
+
+emptyAuth is true if the key has well known authorization "".  If it
+is false or not present, the key requires an explicit authorization
+phrase.  This is used by most user space consumers to decide whether
+to prompt for a password.
+
+parent represents the parent key handle, either in the 0x81 MSO space,
+like 0x81000001 for the RSA primary storage key.  Userspace programmes
+also support specifying the primary handle in the 0x40 MSO space.  If
+this happens the Elliptic Curve variant of the primary key using the
+TCG defined template will be generated on the fly into a volatile
+object and used as the parent.  The current kernel code only supports
+the 0x81 MSO form.
+
+pubkey is the binary representation of TPM2B_PRIVATE excluding the
+initial TPM2B header, which can be reconstructed from the ASN.1 octet
+string length.
+
+privkey is the binary representation of TPM2B_PUBLIC excluding the
+initial TPM2B header which can be reconstructed from the ASN.1 octed
+string length.
+
+DCP Blob Format
+---------------
+
+.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
+   :doc: dcp blob format
+
+.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
+   :identifiers: struct dcp_blob_fmt