[PATCH] media: dvb-core: fix feed leak on failed DMX_ADD_PID

[Rituparna Warwatkar]

dvb_dmxdev_add_pid() allocates a new dmxdev_feed, links it into
filter->feed.ts and, when the filter is already running, immediately
starts the feed.

If starting the feed fails, the newly allocated feed remains on the
list. Subsequent restart and rollback paths may then operate on this
stale entry, leaving feed resources allocated and causing leaks in
drivers that allocate resources from ->start_feed() and release them
from ->stop_feed().

Remove the feed from the list and free it when
dvb_dmxdev_start_feed() fails.

Reported-by: syzbot+e9a1f5e196de6663631b@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=e9a1f5e196de6663631b
Signed-off-by: Rituparna Warwatkar <rwarwatkar@xxxxxxxxx>
---
 drivers/media/dvb-core/dmxdev.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c
index 3c8bc75e4d6..6a825d9bae4 100644
--- a/drivers/media/dvb-core/dmxdev.c
+++ b/drivers/media/dvb-core/dmxdev.c
@@ -884,6 +884,7 @@ static int dvb_dmxdev_add_pid(struct dmxdev *dmxdev,
 			      struct dmxdev_filter *filter, u16 pid)
 {
 	struct dmxdev_feed *feed;
+	int ret;
 
 	if ((filter->type != DMXDEV_TYPE_PES) ||
 	    (filter->state < DMXDEV_STATE_SET))
@@ -901,8 +902,14 @@ static int dvb_dmxdev_add_pid(struct dmxdev *dmxdev,
 	feed->pid = pid;
 	list_add(&feed->next, &filter->feed.ts);
 
-	if (filter->state >= DMXDEV_STATE_GO)
-		return dvb_dmxdev_start_feed(dmxdev, filter, feed);
+	if (filter->state >= DMXDEV_STATE_GO) {
+		ret = dvb_dmxdev_start_feed(dmxdev, filter, feed);
+		if (ret < 0) {
+			list_del(&feed->next);
+			kfree(feed);
+			return ret;
+		}
+	}
 
 	return 0;
 }
-- 
2.47.3