perf: Fix race between perf_event_exit_task() and perf_pending_task()

Overview

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

perf: Fix race between perf_event_exit_task() and perf_pending_task()

A race condition exists between perf_event_exit_task() and perf_pending_task() during begin_new_exec().

During begin_new_exec(), perf_event_exit_task() may be called, and the PF_EXITING flag is not set on task. So perf_sigtrap() continues to execute and triggers WARN_ON_ONCE(event->ctx->task != current).

Since both task exit and exec paths can call perf_event_exit_task() which sets ctx->task to TASK_TOMBSTONE, fix this by explicitly checking if event->ctx->task equals TASK_TOMBSTONE and dropping the redundant PF_EXITING check.

Affected

• Linux >= 97ba62b278674293762c3d91f724f1bb922f04e0 < 672b8a9ce8f51b991481dfde26fba5cc4340a91a
• Linux >= 97ba62b278674293762c3d91f724f1bb922f04e0 < 524063fea29f8a841e49927ea7a8085194ad3ec2
• Linux >= 97ba62b278674293762c3d91f724f1bb922f04e0 < 81e61e3f8befa1bae3ec8e779d8ada5e5e362c21
• Linux >= 97ba62b278674293762c3d91f724f1bb922f04e0 < ffb684f2aa141eeb0caa6308422e7e05d1ded7c4
• Linux 5.13

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.