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: Alexey Khoroshilov <khoroshilov@xxxxxxxxx>
---
drivers/media/dvb-core/dvb_demux.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/media/dvb-core/dvb_demux.c b/drivers/media/dvb-core/dvb_demux.c
index 3485655..6de3bd0 100644
--- a/drivers/media/dvb-core/dvb_demux.c
+++ b/drivers/media/dvb-core/dvb_demux.c
@@ -1027,8 +1027,13 @@ 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;
--
1.8.1.2
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