diff options
| author | Laurent Pinchart | 2014-11-01 10:32:28 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab | 2014-12-04 12:41:11 -0200 |
| commit | f6cee18858b3c0adaa30cbe45a1766c8ef053c5d (patch) | |
| tree | 9b8da082484a7f90c4da7bc7e425f254ceb92c0f /drivers/media | |
| parent | b518d86609cc066b626120fe6ec6fe3a4ccfcd54 (diff) | |
[media] v4l: vb2: Fix race condition in vb2_fop_poll
The vb2_fop_poll() implementation tries to be clever on whether it needs
to lock the queue mutex by checking whether polling might start fileio.
The test requires reading the q->num_buffer field, which is racy if we
don't hold the queue mutex in the first place.
Remove the extra cleverness and just lock the mutex.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/v4l2-core/videobuf2-core.c | 27 |
1 files changed, 8 insertions, 19 deletions
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c index 7aed8f22e075..2685670b20ec 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -3459,27 +3459,16 @@ unsigned int vb2_fop_poll(struct file *file, poll_table *wait) struct video_device *vdev = video_devdata(file); struct vb2_queue *q = vdev->queue; struct mutex *lock = q->lock ? q->lock : vdev->lock; - unsigned long req_events = poll_requested_events(wait); unsigned res; void *fileio; - bool must_lock = false; - - /* Try to be smart: only lock if polling might start fileio, - otherwise locking will only introduce unwanted delays. */ - if (q->num_buffers == 0 && !vb2_fileio_is_active(q)) { - if (!V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_READ) && - (req_events & (POLLIN | POLLRDNORM))) - must_lock = true; - else if (V4L2_TYPE_IS_OUTPUT(q->type) && (q->io_modes & VB2_WRITE) && - (req_events & (POLLOUT | POLLWRNORM))) - must_lock = true; - } - /* If locking is needed, but this helper doesn't know how, then you - shouldn't be using this helper but you should write your own. */ - WARN_ON(must_lock && !lock); + /* + * If this helper doesn't know how to lock, then you shouldn't be using + * it but you should write your own. + */ + WARN_ON(!lock); - if (must_lock && lock && mutex_lock_interruptible(lock)) + if (lock && mutex_lock_interruptible(lock)) return POLLERR; fileio = q->fileio; @@ -3487,9 +3476,9 @@ unsigned int vb2_fop_poll(struct file *file, poll_table *wait) res = vb2_poll(vdev->queue, file, wait); /* If fileio was started, then we have a new queue owner. */ - if (must_lock && !fileio && q->fileio) + if (!fileio && q->fileio) q->owner = file->private_data; - if (must_lock && lock) + if (lock) mutex_unlock(lock); return res; } |