Suren Baghdasaryan 2fd752ed77 psi: Fix uaf issue when psi trigger is destroyed while being polled ... commit a06247c680 upstream. 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: 0e94682b73 ("psi: introduce psi monitor") Reported-by: syzbot+cdb5dd11c97cc532efad@syzkaller.appspotmail.com Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Analyzed-by: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Eric Biggers <ebiggers@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20220111232309.1786347-1-surenb@google.com [surenb: backported to 5.4 kernel] CC: stable@vger.kernel.org # 5.4 Signed-off-by: Suren Baghdasaryan <surenb@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-02-05 12:35:36 +01:00
..
cgroupstats.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00
delay-accounting.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00
index.rst	docs: add some documentation dirs to the driver-api book	2019-07-15 11:03:02 -03:00
psi.rst	psi: Fix uaf issue when psi trigger is destroyed while being polled	2022-02-05 12:35:36 +01:00
taskstats-struct.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00
taskstats.rst	docs: accounting: convert to ReST	2019-07-15 09:20:25 -03:00