Merge tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Don't destroy user event fields when removal fails

   User event fields are destroyed before the event is removed from
   visibility. But that can fail leaving the still visible event with no
   fields. Move the destroying of the fields to after the event is
   successfully removed from visibility.

 - Initialize function graph state is fork before calling
   copy_exec_state()

   For non-CLONE_VM forks, copy_exec_state() allocates a new
   task_exec_state. If that allocation fails, ftrace_graph_exit_task()
   will free the tasks ret_stack pointer. Since that pointer is still
   using the parent's ret_stack, it mistakenly frees the parent's
   pointer too.

   Call ftrace_graph_init() on the task first which will NULL out the
   new tasks's ret_stack and if the copy fails, it will not free
   anything.

 - Remove FGRAPH_MAX_INDEX

   The macro FGRAPH_MAX_INDEX was added but never used. Remove it.

 - Save ent_size in function graph printing of nested functions

   The function graph tracer needs to look at the next event to see if
   the next event is the return of the current function entry. If it is,
   it prints a single line:

	ktime_get();

   Otherwise it prints it like a nested function:

	tick_nohz_irq_exit() {
	    ktime_get();
	    kcpustat_irq_exit();
	}

   In order to look at the next event, it must save the current event so
   that it has the information to print from it. It saves the event in
   the iterator descriptor called "ent". What it doesn't save is the
   ent_size of the event which is now used to know if the function graph
   arguments are to be printed. The peek doesn't save the size so the
   size used happens to be that of the size of the last event that was
   seen.

   Save the entry event size in the iterator descriptor so that the
   correct size is used.

 - Fix several errors with freeing data in the histogram code

   The histogram code had a lot of leaked or or incorrect accounting
   when failures happen. Correct them.

 - Fix histogram regression of .percent and .graph modifiers

   Up until 6.3 histogram values could have "percent" or "graph"
   modifiers that changed how they were printed. But a change that added
   restricting histograms values from being strings, stack traces and
   other modifiers inadvertently prevented them from using the percent
   and graph modifiers, which were legal use cases for values.

   Put back the percent and graph modifiers.

 - Fix various typos in the comments

 - Set the trace_clock before initializing a histogram with clock
   argument

   The histogram API allows the user to specific which trace clock to
   use via a "clock=" string. The histogram is set up first before the
   clock is checked. If the passed in clock is not valid, it exits
   without fully fixing up the histogram leaving it on the list and a
   use-after-free can trigger.

   Update the clock argument first and if it fails then exit gracefully
   before the histogram trigger is placed on any lists.

 - Restore :mod: trailer after parsing in ftrace_set_clr_event

   The function ftrace_set_clr_event() modifies the parse string and
   needs to put it back to what was passed in. It searches for ":mod:"
   via a strsep() but fails to put back the first ':' in the string.

   Add back the ':' in the passed in string.

 - Take trace_array reference when opening a tracer options file

   The options files are dynamically created and some tracers add their
   own options. When a tracer adds their own list of options, the
   trace_array holding them has an array to hold the list of options for
   each tracer. This array increases in size via a krealloc(), and the
   new entry gets a newly allocated array to hold the options of the new
   tracer being added.

   The element in each entry of the tracer's option array holds a
   pointer back to the trace_array, a pointer to the tracer it is
   associated to, a pointer to the flags of the option.

   The issue is that these arrays are freed when the trace_array is
   freed when its instance it represents is removed from the instances
   directory. There's a race that an open of one of these options files
   can happen when the instance is being removed.

   Add a new helper function to be called by the open function of the
   options file to iterate all existing trace_arrays under a lock and
   find the one that has the given option element in one of it's tracer
   arrays. If found, then update the associated trace_array's reference
   counter to keep it from being freed. If not found, have the open call
   return -ENODEV.

 - Disable interrupts when acquiring the lock in rb_wake_up_waiters()

   The function rb_wake_up_waiters() assumes it will be called in
   interrupt context and does not disable irqs when taking
   cpu_buffer->reader_lock, which can be called in hard interrupt
   context. The issue is in PREEMPT_RT, this function is called in
   thread context leaving this lock open to a deadlock.

   Take the lock with interrupts disabled.

 - Use rcu_assign_pointer() for tmp_ops filter hash

   The tmp_ops used in update_ftrace_direct_mod() assigns its
   filter_hash field directly, but that field is annotated as __rcu and
   sparse complains. Assign it with rcu_assign_pointer()

 - Fix use-after-free in enable_trigger_private_data_free()

   The trace_event_call is accessed through the event_trigger_data's
   trace_event_file pointer to put the trace_event_call on freeing. The
   issue is that the trace_event_file data may have been freed already
   causing a use-after-free. Add a field to the event_trigger_data that
   points directly to the trace_event_call so that it can decrement its
   reference directly without needing to go through the
   trace_event_file.

 - Fix accounting of buffer data remote headers

   trace_buffer_desc_size() and trace_remote_alloc_buffer() undercount
   the number of pages is needed for the asked for size as it doesn't
   take into account the meta data on each page. Add a helper function
   to do the calculation properly and use that in these functions.

 - Catch nr_page_va overflow in ring_buffer_desc sizing

   The number of pages per remote ring buffer is capped by
   ring_buffer_desc::nr_page_va (32 bits). A buffer_size large enough to
   overflow that field would silently allocate a descriptor smaller than
   what was asked for.

 - Do not resize the subbuf order if any per_cpu buffer is disabled

   The mmapping of ring buffers disables resizing the subbuffers, but it
   is done per-cpu whereas the subbuf size change is done for all the
   per_cpu buffers under the buffer->mutex. It could change the size of
   some while the mapping is happening on others. Have the resize of the
   subbuf order check all the per_cpu buffers under the lock to see if
   any of them is disabled before starting and causing an inconsistency
   between buffers that are being mapped.

* tag 'trace-v7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: (25 commits)
  ring-buffer: Check resize_disabled before publishing the new subbuf order
  tracing/remotes: Catch nr_page_va overflow in ring_buffer_desc sizing
  tracing/remotes: Account for ring buffer page header in size calculation
  tracing: Don't dereference trace_event_file in deferred trigger free
  ftrace: Use rcu_assign_pointer() for tmp_ops filter hash
  ring-buffer: Acquire the lock with irqsave in rb_wake_up_waiters()
  tracing: Take trace_array reference when opening a tracer options file
  tracing: Fix ring_buffer_read_page_size() kernel-doc
  tracing: Restore :mod: trailer after parsing in ftrace_set_clr_event()
  tracing: Fix memory corruption from a "STACKTRACE" histogram key
  tracing: Fix memory corruption from the histogram stacktrace modifier
  tracing: Undo the registration when enabling the histogram trigger fails
  tracing: Take the reference before publishing the named histogram trigger
  tracing: Set the trace clock before registering the histogram trigger
  tracing: Fix typo "preceeded" in comment
  tracing: Fix typo "availabe" in comment
  tracing: Let histogram values keep the percent and graph modifiers
  tracing: Keep the entry count when the histogram stats allocation fails
  tracing: Free histogram the field rejected for a bad modifier
  tracing: Free histogram the var ref when its initialization fails
  ...

1 files changed, 374 insertions, 0 deletions

diff --git a/Documentation/admin-guide/sysctl/fs.rst b/Documentation/admin-guide/sysctl/fs.rst
new file mode 100644
index 000000000..9b7f65c3e
--- /dev/null
+++ b/Documentation/admin-guide/sysctl/fs.rst
@@ -0,0 +1,374 @@
+===============================
+Documentation for /proc/sys/fs/
+===============================
+
+Copyright (c) 1998, 1999,  Rik van Riel <riel@nl.linux.org>
+
+Copyright (c) 2009,        Shen Feng<shen@cn.fujitsu.com>
+
+For general info and legal blurb, please look in intro.rst.
+
+------------------------------------------------------------------------------
+
+This file contains documentation for the sysctl files and directories
+in ``/proc/sys/fs/``.
+
+The files in this directory can be used to tune and monitor
+miscellaneous and general things in the operation of the Linux
+kernel. Since some of the files *can* be used to screw up your
+system, it is advisable to read both documentation and source
+before actually making adjustments.
+
+1. /proc/sys/fs
+===============
+
+Currently, these files might (depending on your configuration)
+show up in ``/proc/sys/fs``:
+
+.. contents:: :local:
+
+
+aio-nr & aio-max-nr
+-------------------
+
+``aio-nr`` shows the current system-wide number of asynchronous io
+requests.  ``aio-max-nr`` allows you to change the maximum value
+``aio-nr`` can grow to.  If ``aio-nr`` reaches ``aio-nr-max`` then
+``io_setup`` will fail with ``EAGAIN``.  Note that raising
+``aio-max-nr`` does not result in the
+pre-allocation or re-sizing of any kernel data structures.
+
+dentry-negative
+----------------------------
+
+Policy for negative dentries. Set to 1 to always delete the dentry when a
+file is removed, and 0 to disable it. By default, this behavior is disabled.
+
+dentry-state
+------------
+
+This file shows the values in ``struct dentry_stat_t``, as defined in
+``fs/dcache.c``::
+
+  struct dentry_stat_t dentry_stat {
+        long nr_dentry;
+        long nr_unused;
+        long age_limit;         /* age in seconds */
+        long want_pages;        /* pages requested by system */
+        long nr_negative;       /* # of unused negative dentries */
+        long dummy;             /* Reserved for future use */
+  };
+
+Dentries are dynamically allocated and deallocated.
+
+``nr_dentry`` shows the total number of dentries allocated (active
++ unused). ``nr_unused shows`` the number of dentries that are not
+actively used, but are saved in the LRU list for future reuse.
+
+``age_limit`` is the age in seconds after which dcache entries
+can be reclaimed when memory is short and ``want_pages`` is
+nonzero when ``shrink_dcache_pages()`` has been called and the
+dcache isn't pruned yet.
+
+``nr_negative`` shows the number of unused dentries that are also
+negative dentries which do not map to any files. Instead,
+they help speeding up rejection of non-existing files provided
+by the users.
+
+
+file-max & file-nr
+------------------
+
+The value in ``file-max`` denotes the maximum number of file-
+handles that the Linux kernel will allocate. When you get lots
+of error messages about running out of file handles, you might
+want to increase this limit.
+
+Historically,the kernel was able to allocate file handles
+dynamically, but not to free them again. The three values in
+``file-nr`` denote the number of allocated file handles, the number
+of allocated but unused file handles, and the maximum number of
+file handles. Linux 2.6 and later always reports 0 as the number of free
+file handles -- this is not an error, it just means that the
+number of allocated file handles exactly matches the number of
+used file handles.
+
+Attempts to allocate more file descriptors than ``file-max`` are
+reported with ``printk``, look for::
+
+  VFS: file-max limit <number> reached
+
+in the kernel logs.
+
+
+inode-nr & inode-state
+----------------------
+
+As with file handles, the kernel allocates the inode structures
+dynamically, but can't free them yet.
+
+The file ``inode-nr`` contains the first two items from
+``inode-state``, so we'll skip to that file...
+
+``inode-state`` contains three actual numbers and four dummies.
+The actual numbers are, in order of appearance, ``nr_inodes``,
+``nr_free_inodes`` and ``preshrink``.
+
+``nr_inodes`` stands for the number of inodes the system has
+allocated.
+
+``nr_free_inodes`` represents the number of free inodes (?) and
+preshrink is nonzero when the
+system needs to prune the inode list instead of allocating
+more.
+
+
+mount-max
+---------
+
+This denotes the maximum number of mounts that may exist
+in a mount namespace.
+
+
+nr_open
+-------
+
+This denotes the maximum number of file-handles a process can
+allocate. Default value is 1024*1024 (1048576) which should be
+enough for most machines. Actual limit depends on ``RLIMIT_NOFILE``
+resource limit.
+
+
+overflowgid & overflowuid
+-------------------------
+
+Some filesystems only support 16-bit UIDs and GIDs, although in Linux
+UIDs and GIDs are 32 bits. When one of these filesystems is mounted
+with writes enabled, any UID or GID that would exceed 65535 is translated
+to a fixed value before being written to disk.
+
+These sysctls allow you to change the value of the fixed UID and GID.
+The default is 65534.
+
+
+pipe-user-pages-hard
+--------------------
+
+Maximum total number of pages a non-privileged user may allocate for pipes.
+Once this limit is reached, no new pipes may be allocated until usage goes
+below the limit again. When set to 0, no limit is applied, which is the default
+setting.
+
+
+pipe-user-pages-soft
+--------------------
+
+Maximum total number of pages a non-privileged user may allocate for pipes
+before the pipe size gets limited to two pages. Once this limit is reached,
+new pipes will be limited to two pages in size for this user in order to
+limit total memory usage, and trying to increase them using ``fcntl()`` will be
+denied until usage goes below the limit again. The default value allows to
+allocate up to 1024 pipes at their default size. When set to 0, no limit is
+applied.
+
+
+protected_fifos
+---------------
+
+The intent of this protection is to avoid unintentional writes to
+an attacker-controlled FIFO, where a program expected to create a regular
+file.
+
+When set to "0", writing to FIFOs is unrestricted.
+
+When set to "1" don't allow ``O_CREAT`` open on FIFOs that we don't own
+in world writable sticky directories, unless they are owned by the
+owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+This protection is based on the restrictions in Openwall.
+
+
+protected_hardlinks
+--------------------
+
+A long-standing class of security issues is the hardlink-based
+time-of-check-time-of-use race, most commonly seen in world-writable
+directories like ``/tmp``. The common method of exploitation of this flaw
+is to cross privilege boundaries when following a given hardlink (i.e. a
+root process follows a hardlink created by another user). Additionally,
+on systems without separated partitions, this stops unauthorized users
+from "pinning" vulnerable setuid/setgid files against being upgraded by
+the administrator, or linking to special files.
+
+When set to "0", hardlink creation behavior is unrestricted.
+
+When set to "1" hardlinks cannot be created by users if they do not
+already own the source file, or do not have read/write access to it.
+
+This protection is based on the restrictions in Openwall and grsecurity.
+
+
+protected_regular
+-----------------
+
+This protection is similar to `protected_fifos`_, but it
+avoids writes to an attacker-controlled regular file, where a program
+expected to create one.
+
+When set to "0", writing to regular files is unrestricted.
+
+When set to "1" don't allow ``O_CREAT`` open on regular files that we
+don't own in world writable sticky directories, unless they are
+owned by the owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+
+protected_symlinks
+------------------
+
+A long-standing class of security issues is the symlink-based
+time-of-check-time-of-use race, most commonly seen in world-writable
+directories like ``/tmp``. The common method of exploitation of this flaw
+is to cross privilege boundaries when following a given symlink (i.e. a
+root process follows a symlink belonging to another user). For a likely
+incomplete list of hundreds of examples across the years, please see:
+https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp
+
+When set to "0", symlink following behavior is unrestricted.
+
+When set to "1" symlinks are permitted to be followed only when outside
+a sticky world-writable directory, or when the uid of the symlink and
+follower match, or when the directory owner matches the symlink's owner.
+
+This protection is based on the restrictions in Openwall and grsecurity.
+
+
+suid_dumpable
+-------------
+
+This value can be used to query and set the core dump mode for setuid
+or otherwise protected/tainted binaries. The modes are
+
+=   ==========  ===============================================================
+0   (default)	Traditional behaviour. Any process which has changed
+		privilege levels or is execute only will not be dumped.
+1   (debug)	All processes dump core when possible. The core dump is
+		owned by the current user and no security is applied. This is
+		intended for system debugging situations only.
+		Ptrace is unchecked.
+		This is insecure as it allows regular users to examine the
+		memory contents of privileged processes.
+2   (suidsafe)	Any binary which normally would not be dumped is dumped
+		anyway, but only if the ``core_pattern`` kernel sysctl (see
+		:ref:`Documentation/admin-guide/sysctl/kernel.rst <core_pattern>`)
+		is set to
+		either a pipe handler or a fully qualified path. (For more
+		details on this limitation, see CVE-2006-2451.) This mode is
+		appropriate when administrators are attempting to debug
+		problems in a normal environment, and either have a core dump
+		pipe handler that knows to treat privileged core dumps with
+		care, or specific directory defined for catching core dumps.
+		If a core dump happens without a pipe handler or fully
+		qualified path, a message will be emitted to syslog warning
+		about the lack of a correct setting.
+=   ==========  ===============================================================
+
+
+
+2. /proc/sys/fs/binfmt_misc
+===========================
+
+Documentation for the files in ``/proc/sys/fs/binfmt_misc`` is
+in Documentation/admin-guide/binfmt-misc.rst.
+
+
+3. /proc/sys/fs/mqueue - POSIX message queues filesystem
+========================================================
+
+
+The "mqueue"  filesystem provides  the necessary kernel features to enable the
+creation of a  user space  library that  implements  the  POSIX message queues
+API (as noted by the  MSG tag in the  POSIX 1003.1-2001 version  of the System
+Interfaces specification.)
+
+The "mqueue" filesystem contains values for determining/setting the
+amount of resources used by the file system.
+
+``/proc/sys/fs/mqueue/queues_max`` is a read/write file for
+setting/getting the maximum number of message queues allowed on the
+system.
+
+``/proc/sys/fs/mqueue/msg_max`` is a read/write file for
+setting/getting the maximum number of messages in a queue value.  In
+fact it is the limiting value for another (user) limit which is set in
+``mq_open`` invocation.  This attribute of a queue must be less than
+or equal to ``msg_max``.
+
+``/proc/sys/fs/mqueue/msgsize_max`` is a read/write file for
+setting/getting the maximum message size value (it is an attribute of
+every message queue, set during its creation).
+
+``/proc/sys/fs/mqueue/msg_default`` is a read/write file for
+setting/getting the default number of messages in a queue value if the
+``attr`` parameter of ``mq_open(2)`` is ``NULL``. If it exceeds
+``msg_max``, the default value is initialized to ``msg_max``.
+
+``/proc/sys/fs/mqueue/msgsize_default`` is a read/write file for
+setting/getting the default message size value if the ``attr``
+parameter of ``mq_open(2)`` is ``NULL``. If it exceeds
+``msgsize_max``, the default value is initialized to ``msgsize_max``.
+
+4. /proc/sys/fs/epoll - Configuration options for the epoll interface
+=====================================================================
+
+This directory contains configuration options for the epoll(7) interface.
+
+max_user_watches
+----------------
+
+Every epoll file descriptor can store a number of files to be monitored
+for event readiness. Each one of these monitored files constitutes a "watch".
+This configuration option sets the maximum number of "watches" that are
+allowed for each user.
+Each "watch" costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes
+on a 64-bit one.
+The current default value for ``max_user_watches`` is 4% of the
+available low memory, divided by the "watch" cost in bytes.
+
+5. /proc/sys/fs/fuse - Configuration options for FUSE filesystems
+=====================================================================
+
+This directory contains the following configuration options for FUSE
+filesystems:
+
+``/proc/sys/fs/fuse/max_pages_limit`` is a read/write file for
+setting/getting the maximum number of pages that can be used for servicing
+requests in FUSE.
+
+``/proc/sys/fs/fuse/default_request_timeout`` is a read/write file for
+setting/getting the default timeout (in seconds) for a fuse server to
+reply to a kernel-issued request in the event where the server did not
+specify a timeout at mount. If the server set a timeout,
+then default_request_timeout will be ignored.  The default
+"default_request_timeout" is set to 0. 0 indicates no default timeout.
+The maximum value that can be set is 65535.
+
+``/proc/sys/fs/fuse/max_request_timeout`` is a read/write file for
+setting/getting the maximum timeout (in seconds) for a fuse server to
+reply to a kernel-issued request. A value greater than 0 automatically opts
+the server into a timeout that will be set to at most "max_request_timeout",
+even if the server did not specify a timeout and default_request_timeout is
+set to 0. If max_request_timeout is greater than 0 and the server set a timeout
+greater than max_request_timeout or default_request_timeout is set to a value
+greater than max_request_timeout, the system will use max_request_timeout as the
+timeout. 0 indicates no max request timeout. The maximum value that can be set
+is 65535.
+
+For timeouts, if the server does not respond to the request by the time
+the set timeout elapses, then the connection to the fuse server will be aborted.
+Please note that the timeouts are not 100% precise (eg you may set 60 seconds but
+the timeout may kick in after 70 seconds). The upper margin of error for the
+timeout is roughly FUSE_TIMEOUT_TIMER_FREQ seconds.