On Tue, Jan 11, 2022 at 03:23:09PM -0800, Suren Baghdasaryan wrote:
With write operation on psi files replacing old trigger with a new one, the lifetime of its waitqueue is totally arbitrary. Overwriting an existing trigger causes its waitqueue to be freed and pending poll() will stumble on trigger->event_wait which was destroyed. Fix this by disallowing to redefine an existing psi trigger. If a write operation is used on a file descriptor with an already existing psi trigger, the operation will fail with EBUSY error. Also bypass a check for psi_disabled in the psi_trigger_destroy as the flag can be flipped after the trigger is created, leading to a memory leak.
Fixes: 0e94682b73bf ("psi: introduce psi monitor") Cc: stable@vger.kernel.org Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Analyzed-by: Eric Biggers ebiggers@kernel.org Suggested-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Suren Baghdasaryan surenb@google.com
Acked-by: Johannes Weiner hannes@cmpxchg.org