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, 101 insertions, 0 deletions

diff --git a/Documentation/security/digsig.rst b/Documentation/security/digsig.rst
new file mode 100644
index 000000000..de035f282
--- /dev/null
+++ b/Documentation/security/digsig.rst
@@ -0,0 +1,101 @@
+==================================
+Digital Signature Verification API
+==================================
+
+:Author: Dmitry Kasatkin
+:Date: 06.10.2011
+
+
+.. CONTENTS
+
+   1. Introduction
+   2. API
+   3. User-space utilities
+
+
+Introduction
+============
+
+Digital signature verification API provides a method to verify digital signature.
+Currently digital signatures are used by the IMA/EVM integrity protection subsystem.
+
+Digital signature verification is implemented using cut-down kernel port of
+GnuPG multi-precision integers (MPI) library. The kernel port provides
+memory allocation errors handling, has been refactored according to kernel
+coding style, and checkpatch.pl reported errors and warnings have been fixed.
+
+Public key and signature consist of header and MPIs::
+
+	struct pubkey_hdr {
+		uint8_t		version;	/* key format version */
+		time_t		timestamp;	/* key made, always 0 for now */
+		uint8_t		algo;
+		uint8_t		nmpi;
+		char		mpi[0];
+	} __packed;
+
+	struct signature_hdr {
+		uint8_t		version;	/* signature format version */
+		time_t		timestamp;	/* signature made */
+		uint8_t		algo;
+		uint8_t		hash;
+		uint8_t		keyid[8];
+		uint8_t		nmpi;
+		char		mpi[0];
+	} __packed;
+
+keyid equals to SHA1[12-19] over the total key content.
+Signature header is used as an input to generate a signature.
+Such approach insures that key or signature header could not be changed.
+It protects timestamp from been changed and can be used for rollback
+protection.
+
+API
+===
+
+API currently includes only 1 function::
+
+	digsig_verify() - digital signature verification with public key
+
+
+	/**
+	* digsig_verify() - digital signature verification with public key
+	* @keyring:	keyring to search key in
+	* @sig:	digital signature
+	* @sigen:	length of the signature
+	* @data:	data
+	* @datalen:	length of the data
+	* @return:	0 on success, -EINVAL otherwise
+	*
+	* Verifies data integrity against digital signature.
+	* Currently only RSA is supported.
+	* Normally hash of the content is used as a data for this function.
+	*
+	*/
+	int digsig_verify(struct key *keyring, const char *sig, int siglen,
+			  const char *data, int datalen);
+
+User-space utilities
+====================
+
+The signing and key management utilities evm-utils provide functionality
+to generate signatures, to load keys into the kernel keyring.
+Keys can be in PEM or converted to the kernel format.
+When the key is added to the kernel keyring, the keyid defines the name
+of the key: 5D2B05FC633EE3E8 in the example below.
+
+Here is example output of the keyctl utility::
+
+	$ keyctl show
+	Session Keyring
+	-3 --alswrv      0     0  keyring: _ses
+	603976250 --alswrv      0    -1   \_ keyring: _uid.0
+	817777377 --alswrv      0     0       \_ user: kmk
+	891974900 --alswrv      0     0       \_ encrypted: evm-key
+	170323636 --alswrv      0     0       \_ keyring: _module
+	548221616 --alswrv      0     0       \_ keyring: _ima
+	128198054 --alswrv      0     0       \_ keyring: _evm
+
+	$ keyctl list 128198054
+	1 key in keyring:
+	620789745: --alswrv     0     0 user: 5D2B05FC633EE3E8