Commit 6633327d authored by Alexey Khoroshilov's avatar Alexey Khoroshilov Committed by Mauro Carvalho Chehab

[media] dvb_demux: fix deadlock in dmx_section_feed_release_filter()

dmx_section_feed_release_filter() locks dvbdmx->mutex and
if the feed is still filtering, it calls feed->stop_filtering(feed).
stop_filtering() is implemented by dmx_section_feed_stop_filtering()
that first of all try to lock the same mutex: dvbdmx->mutex.
That leads to a deadlock.
It does not happen often in practice because all callers of
release_filter() stop filtering by themselves.
So the problem can happen in case of race condition only.
The patch releases dvbdmx->mutex before call to feed->stop_filtering(feed)
and reacquires the mutex after that.
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: default avatarAlexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: default avatarMichael Krufky <mkrufky@linuxtv.org>
Signed-off-by: default avatarMauro Carvalho Chehab <m.chehab@samsung.com>
parent 858559a2
......@@ -1032,8 +1032,13 @@ static int dmx_section_feed_release_filter(struct dmx_section_feed *feed,
return -EINVAL;
}
if (feed->is_filtering)
if (feed->is_filtering) {
/* release dvbdmx->mutex as far as
it is acquired by stop_filtering() itself */
mutex_unlock(&dvbdmx->mutex);
feed->stop_filtering(feed);
mutex_lock(&dvbdmx->mutex);
}
spin_lock_irq(&dvbdmx->lock);
f = dvbdmxfeed->filter;
......
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