CVE-2026-93191smack: fix incorrect task context in smack_msg_queue_msgrcv

Official description

In the Linux kernel, the following vulnerability has been resolved: smack: fix incorrect task context in smack_msg_queue_msgrcv The smack_msg_queue_msgrcv() function incorrectly checks the permissions of the 'current' task instead of the 'target' task. In the msgsnd() syscall path, if a receiver is already waiting, the pipelined_send() optimization is used to push the message directly to the receiver task: ipc/msg.c`pipelined_send(): ` smp_store_release(&msr->r_msg, msg) In this case, the 'sender' (current) task performs the check on behalf of the 'receiver' task (msr->r_tsk, passed as the 'target' parameter): ipc/msg.c`pipelined_send(): ` security_msg_queue_msgrcv(,, target := msr->r_tsk,,) However, smack_msg_queue_msgrcv() ignores the 'target' and checks 'current': smack_msg_queue_msgrcv(…) ` smk_curacc_msq(isp, MAY_READWRITE); // current task 'current' MAY satisfy smack_msg_queue_msgrcv r/w requirement, but 'target' (the receiver task) might NOT; as a result, an unauthorized receiver gets the message, violating MAC policy. Test: 1) create a sysv message queue with label “foo” 2) echo "bar foo r" >/smack/load2 3) msgrcv(,,,0,MSG_NOERROR) in "bar"-labeled task. The task is waiting for the messages ... 4) msgsnd() from a "foo"-labeled task: "bar"-labeled task gets the message. This patch fixes the issue by checking permission on the 'target' task instead of 'current'. (2008-02-04, Casey Schaufler)

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/4e49f997ef0c569e09b42aab6bd38c7c54ea095d
• https://git.kernel.org/stable/c/dbece6c2f80b0470d8d99d7a016827dce99ed6e3
• https://git.kernel.org/stable/c/7be4bd21c50afa83c93799b0f16cf5bfa493194e
• https://git.kernel.org/stable/c/ec47f4177046dfaaf1cebb15f4d2e7b543475daf
• https://git.kernel.org/stable/c/e35dc5a4ed6d1e536382d80c685187511ff248a1
• https://git.kernel.org/stable/c/c2ab27c2e11591524b1378c24ad18882a425d1fa
• https://git.kernel.org/stable/c/d02c55e3ea82e41ea2c2026e08201e5daa4d0cfe
• https://git.kernel.org/stable/c/fba3d32825f4bbc8e20f0cdc3b14df57965b8fe5