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Commit 467052f6 authored by Alexander Popov's avatar Alexander Popov Committed by Greg Kroah-Hartman
Browse files

media: vivid: Fix wrong locking that causes race conditions on streaming stop 



commit 6dcd5d7a7a29c1e4b8016a06aed78cd650cd8c27 upstream.

There is the same incorrect approach to locking implemented in
vivid_stop_generating_vid_cap(), vivid_stop_generating_vid_out() and
sdr_cap_stop_streaming().

These functions are called during streaming stopping with vivid_dev.mutex
locked. And they all do the same mistake while stopping their kthreads,
which need to lock this mutex as well. See the example from
vivid_stop_generating_vid_cap():
  /* shutdown control thread */
  vivid_grab_controls(dev, false);
  mutex_unlock(&dev->mutex);
  kthread_stop(dev->kthread_vid_cap);
  dev->kthread_vid_cap = NULL;
  mutex_lock(&dev->mutex);

But when this mutex is unlocked, another vb2_fop_read() can lock it
instead of vivid_thread_vid_cap() and manipulate the buffer queue.
That causes a use-after-free access later.

To fix those issues let's:
  1. avoid unlocking the mutex in vivid_stop_generating_vid_cap(),
vivid_stop_generating_vid_out() and sdr_cap_stop_streaming();
  2. use mutex_trylock() with schedule_timeout_uninterruptible() in
the loops of the vivid kthread handlers.

Signed-off-by: default avatarAlexander Popov <alex.popov@linux.com>
Acked-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: <stable@vger.kernel.org>      # for v3.18 and up
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b73b28b1

drivers/media/platform/vivid/vivid-kthread-cap.c

+5 −3
Original line number Diff line number Diff line
@@ -765,7 +765,11 @@ static int vivid_thread_vid_cap(void *data) 
		if (kthread_should_stop())

			break;



		mutex_lock(&dev->mutex);

		if (!mutex_trylock(&dev->mutex)) {

			schedule_timeout_uninterruptible(1);

			continue;

		}



		cur_jiffies = jiffies;

		if (dev->cap_seq_resync) {

			dev->jiffies_vid_cap = cur_jiffies;
@@ -918,8 +922,6 @@ void vivid_stop_generating_vid_cap(struct vivid_dev *dev, bool *pstreaming) 


	/* shutdown control thread */

	vivid_grab_controls(dev, false);

	mutex_unlock(&dev->mutex);

	kthread_stop(dev->kthread_vid_cap);

	dev->kthread_vid_cap = NULL;

	mutex_lock(&dev->mutex);

}

drivers/media/platform/vivid/vivid-kthread-out.c

+5 −3
Original line number Diff line number Diff line
@@ -135,7 +135,11 @@ static int vivid_thread_vid_out(void *data) 
		if (kthread_should_stop())

			break;



		mutex_lock(&dev->mutex);

		if (!mutex_trylock(&dev->mutex)) {

			schedule_timeout_uninterruptible(1);

			continue;

		}



		cur_jiffies = jiffies;

		if (dev->out_seq_resync) {

			dev->jiffies_vid_out = cur_jiffies;
@@ -289,8 +293,6 @@ void vivid_stop_generating_vid_out(struct vivid_dev *dev, bool *pstreaming) 


	/* shutdown control thread */

	vivid_grab_controls(dev, false);

	mutex_unlock(&dev->mutex);

	kthread_stop(dev->kthread_vid_out);

	dev->kthread_vid_out = NULL;

	mutex_lock(&dev->mutex);

}

drivers/media/platform/vivid/vivid-sdr-cap.c

+5 −3
Original line number Diff line number Diff line
@@ -137,7 +137,11 @@ static int vivid_thread_sdr_cap(void *data) 
		if (kthread_should_stop())

			break;



		mutex_lock(&dev->mutex);

		if (!mutex_trylock(&dev->mutex)) {

			schedule_timeout_uninterruptible(1);

			continue;

		}



		cur_jiffies = jiffies;

		if (dev->sdr_cap_seq_resync) {

			dev->jiffies_sdr_cap = cur_jiffies;
@@ -297,10 +301,8 @@ static void sdr_cap_stop_streaming(struct vb2_queue *vq) 
	}



	/* shutdown control thread */

	mutex_unlock(&dev->mutex);

	kthread_stop(dev->kthread_sdr_cap);

	dev->kthread_sdr_cap = NULL;

	mutex_lock(&dev->mutex);

}



const struct vb2_ops vivid_sdr_cap_qops = {