UBUNTU-CVE-2026-93191: Medium severity ubuntu/linux vulnerability

In the Linux kernel, the following vulnerability has been resolved: smack: fix incorrect task context in smackmsgqueuemsgrcv The smackmsgqueuemsgrcv() 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 pipelinedsend() optimization is used to push the message directly to the receiver task: ipc/msg.cpipelinedsend(): smpstorerelease(&msr->rmsg, msg) In this case, the 'sender' (current) task performs the check on behalf of the 'receiver' task (msr->rtsk, passed as the 'target' parameter): ipc/msg.cpipelinedsend(): securitymsgqueuemsgrcv(,, target := msr->rtsk,,) However, smackmsgqueuemsgrcv() ignores the 'target' and checks 'current': smackmsgqueuemsgrcv(…) smkcuraccmsq(isp, MAYREADWRITE); // current task 'current' MAY satisfy smackmsgqueuemsgrcv 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,MSGNOERROR) 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)