From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- Documentation/security/digsig.rst | 101 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 101 insertions(+) create mode 100644 Documentation/security/digsig.rst (limited to 'Documentation/security/digsig.rst') 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 -- cgit v1.3.1