CVE-2026-74753: perf: Reject exited events as group leaders
In the Linux kernel, the following vulnerability has been resolved:
perf: Reject exited events as group leaders
perfeventremoveonexec() sets remove-on-exec events to the EXIT state and detaches their group relationships. The event's file descriptor can remain open, however, and perfeventopen() currently accepts that event as a group leader because its early validation rejects only REVOKED and DEAD events.
A new sibling can consequently be linked to the detached leader. When the leader is closed, perfgroupdetach() observes that its PERFATTACHGROUP bit is already clear and skips the new sibling. The sibling then retains a groupleader pointer to the freed event.
Reject group leaders in the EXIT state. Perform the check while holding the shared context mutex so that an exec in the target task cannot detach the leader between validation and group attachment.
[peterz: make the earlier test fully consistent]
Affected Software
Event History
Frequently Asked Questions
What conditions are required for exploitation?
An attacker needs an open file descriptor for a perf event configured with remove-on-exec after that event has entered the EXIT state and had its group relationships detached. They must then use that exited event as a group leader when creating a new sibling event, and the leader must subsequently be closed.
What is the resulting failure condition?
The newly created sibling can retain a group_leader pointer to an event that has been freed. This creates a stale pointer condition after the exited leader is closed.
Is this limited to a race during event attachment?
Yes. The issue involves an exec in the target task detaching the leader between validation and group attachment. The fix validates the leader while holding the shared context mutex to prevent that transition during attachment.
How can affected behavior be identified?
Affected systems accept a perf event in the EXIT state as a group leader. The corrected behavior rejects group leaders in the EXIT state.