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authorHans Verkuil <hverkuil@xs4all.nl>2010-11-26 06:54:53 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2010-12-01 20:10:20 -0200
commitca9afe6f87b569cdf8e797395381f18ae23a2905 (patch)
tree9c5475baf2bb90f05fe25e8ca6fa8f53c2fc05dc /drivers/media
parent879aa24d6394aa04b690a600a41ff500441ad384 (diff)
[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.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 6b64fd607b2..359e23290a7 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);