CVE-2024-43869 Information

Description

In the Linux kernel the following vulnerability has been resolved:

perf: Fix event leak upon exec and file release

The perf pending task work is never waited upon the matching event release. In the case of a child event released via free_event() directly this can potentially result in a leaked event such as in the following scenario that doesn’t even require a weak IRQ work implementation to trigger:

schedule() prepare_task_switch() =======> perf_event_overflow() event->pending_sigtrap = … irq_work_queue(&event->pending_irq) <======= perf_event_task_sched_out() event_sched_out() event->pending_sigtrap = 0; atomic_long_inc_not_zero(&event->refcount) task_work_add(&event->pending_task) finish_lock_switch() =======> perf_pending_irq() //do nothing rely on pending task work <=======

begin_new_exec() perf_event_exit_task() perf_event_exit_event() // If is child event free_event() WARN(atomic_long_cmpxchg(&event->refcount 1 0) != 1) // event is leaked

Similar scenarios can also happen with perf_event_remove_on_exec() or simply against concurrent perf_event_release().

Fix this with synchonizing against the possibly remaining pending task work while freeing the event just like is done with remaining pending IRQ work. This means that the pending task callback neither need nor should hold a reference to the event preventing it from ever beeing freed.

Reference

https://git.kernel.org/stable/c/9ad46f1fef421d43cdab3a7d1744b2f43b54dae0 https://git.kernel.org/stable/c/ed2c202dac55423a52d7e2290f2888bf08b8ee99 https://git.kernel.org/stable/c/104e258a004037bc7dba9f6085c71dad6af57ad4 https://git.kernel.org/stable/c/f34d8307a73a18de5320fcc6f40403146d061891 https://git.kernel.org/stable/c/3a5465418f5fd970e86a86c7f4075be262682840