From ad608fbcf166fec809e402d548761768f602702c Mon Sep 17 00:00:00 2001 From: Sakari Ailus Date: Tue, 11 Sep 2018 05:32:37 -0400 Subject: media: v4l: event: Prevent freeing event subscriptions while accessed The event subscriptions are added to the subscribed event list while holding a spinlock, but that lock is subsequently released while still accessing the subscription object. This makes it possible to unsubscribe the event --- and freeing the subscription object's memory --- while the subscription object is simultaneously accessed. Prevent this by adding a mutex to serialise the event subscription and unsubscription. This also gives a guarantee to the callback ops that the add op has returned before the del op is called. This change also results in making the elems field less special: subscriptions are only added to the event list once they are fully initialised. Signed-off-by: Sakari Ailus Reviewed-by: Hans Verkuil Reviewed-by: Laurent Pinchart Cc: stable@vger.kernel.org # for 4.14 and up Fixes: c3b5b0241f62 ("V4L/DVB: V4L: Events: Add backend") Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/v4l2-fh.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/media/v4l2-core/v4l2-fh.c') diff --git a/drivers/media/v4l2-core/v4l2-fh.c b/drivers/media/v4l2-core/v4l2-fh.c index 3895999bf880..c91a7bd3ecfc 100644 --- a/drivers/media/v4l2-core/v4l2-fh.c +++ b/drivers/media/v4l2-core/v4l2-fh.c @@ -45,6 +45,7 @@ void v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev) INIT_LIST_HEAD(&fh->available); INIT_LIST_HEAD(&fh->subscribed); fh->sequence = -1; + mutex_init(&fh->subscribe_lock); } EXPORT_SYMBOL_GPL(v4l2_fh_init); @@ -90,6 +91,7 @@ void v4l2_fh_exit(struct v4l2_fh *fh) return; v4l_disable_media_source(fh->vdev); v4l2_event_unsubscribe_all(fh); + mutex_destroy(&fh->subscribe_lock); fh->vdev = NULL; } EXPORT_SYMBOL_GPL(v4l2_fh_exit); -- cgit v1.2.3