Commit f3b54421 authored May 12, 2023 by Takashi Iwai Committed by Greg Kroah-Hartman Jun 09, 2023

media: dvb-core: Fix kernel WARNING for blocking operation in wait_event*()

[ Upstream commit b8c75e4a1b325ea0a9433fa8834be97b5836b946 ]

Using a semaphore in the wait_event*() condition is no good idea.
It hits a kernel WARN_ON() at prepare_to_wait_event() like:
  do not call blocking ops when !TASK_RUNNING; state=1 set at
  prepare_to_wait_event+0x6d/0x690

For avoiding the potential deadlock, rewrite to an open-coded loop
instead.  Unlike the loop in wait_event*(), this uses wait_woken()
after the condition check, hence the task state stays consistent.

CVE-2023-31084 was assigned to this bug.

Link: https://lore.kernel.org/r/CA+UBctCu7fXn4q41O_3=id1+OdyQ85tZY1x+TkT-6OVBL6KAUw@mail.gmail.com/

Link: https://lore.kernel.org/linux-media/20230512151800.1874-1-tiwai@suse.de


Reported-by: Yu Hao <yhao016@ucr.edu>
Closes: https://nvd.nist.gov/vuln/detail/CVE-2023-31084


Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 7bb9c6e0

drivers/media/dvb-core/dvb_frontend.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -304,14 +304,22 @@ static int dvb_frontend_get_event(struct dvb_frontend *fe,
		}

		if (events->eventw == events->eventr) {
		int ret;
		struct wait_queue_entry wait;
		int ret = 0;

		if (flags & O_NONBLOCK)
		return -EWOULDBLOCK;

		ret = wait_event_interruptible(events->wait_queue,
		dvb_frontend_test_event(fepriv, events));

		init_waitqueue_entry(&wait, current);
		add_wait_queue(&events->wait_queue, &wait);
		while (!dvb_frontend_test_event(fepriv, events)) {
		wait_woken(&wait, TASK_INTERRUPTIBLE, 0);
		if (signal_pending(current)) {
		ret = -ERESTARTSYS;
		break;
		}
		}
		remove_wait_queue(&events->wait_queue, &wait);
		if (ret < 0)
		return ret;
		}