In the Linux kernel, the following vulnerability has been resolved: perf: Fix race between perf_event_exit_task() and perf_pending_task()

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.