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| author | Hans Verkuil <hverkuil@xs4all.nl> | 2010-11-26 06:54:53 -0300 |
|---|---|---|
| committer | Mauro Carvalho Chehab <mchehab@redhat.com> | 2010-12-01 20:10:20 -0200 |
| commit | ca9afe6f87b569cdf8e797395381f18ae23a2905 (patch) | |
| tree | 9c5475baf2bb90f05fe25e8ca6fa8f53c2fc05dc /drivers/media | |
| parent | 879aa24d6394aa04b690a600a41ff500441ad384 (diff) | |
| download | linux-stable-ca9afe6f87b569cdf8e797395381f18ae23a2905.tar.gz linux-stable-ca9afe6f87b569cdf8e797395381f18ae23a2905.tar.bz2 linux-stable-ca9afe6f87b569cdf8e797395381f18ae23a2905.zip | |
[media] v4l2-dev: fix race condition
The unregister function had a race condition with the v4l2_open
function. Ensure that both functions test and clear the REGISTER
flag from within a critical section.
Thanks to Laurent Pinchart for finding this race.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/video/v4l2-dev.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c index 6b64fd607b20..359e23290a7e 100644 --- a/drivers/media/video/v4l2-dev.c +++ b/drivers/media/video/v4l2-dev.c @@ -309,7 +309,7 @@ static int v4l2_open(struct inode *inode, struct file *filp) mutex_lock(&videodev_lock); vdev = video_devdata(filp); /* return ENODEV if the video device has already been removed. */ - if (vdev == NULL) { + if (vdev == NULL || !video_is_registered(vdev)) { mutex_unlock(&videodev_lock); return -ENODEV; } @@ -624,7 +624,12 @@ void video_unregister_device(struct video_device *vdev) if (!vdev || !video_is_registered(vdev)) return; + mutex_lock(&videodev_lock); + /* This must be in a critical section to prevent a race with v4l2_open. + * Once this bit has been cleared video_get may never be called again. + */ clear_bit(V4L2_FL_REGISTERED, &vdev->flags); + mutex_unlock(&videodev_lock); device_unregister(&vdev->dev); } EXPORT_SYMBOL(video_unregister_device); |