ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 73 insertions, 0 deletions

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