Use After Free Affecting kernel-tools-libs package, versions *

Note: Versions mentioned in the description apply only to the upstream kernel-tools-libs package and not the kernel-tools-libs package as distributed by RHEL. See How to fix? for RHEL:8 relevant fixed versions and status.

In the Linux kernel, the following vulnerability has been resolved:

perf: Fix perf_pending_task() UaF

Per syzbot it is possible for perf_pending_task() to run after the event is free()'d. There are two related but distinct cases:

• the task_work was already queued before destroying the event;
• destroying the event itself queues the task_work.

The first cannot be solved using task_work_cancel() since perf_release() itself might be called from a task_work (____fput), which means the current->task_works list is already empty and task_work_cancel() won't be able to find the perf_pending_task() entry.

The simplest alternative is extending the perf_event lifetime to cover the task_work.

The second is just silly, queueing a task_work while you know the event is going away makes no sense and is easily avoided by re-arranging how the event is marked STATE_DEAD and ensuring it goes through STATE_OFF on the way down.

• https://access.redhat.com/security/cve/CVE-2022-48950
• https://git.kernel.org/stable/c/517e6a301f34613bff24a8e35b5455884f2d83d8
• https://git.kernel.org/stable/c/78e1317a174edbfd1182599bf76c092a2877672c
• https://git.kernel.org/stable/c/8bffa95ac19ff27c8261904f89d36c7fcf215d59