On Fri 22-08-14 23:31:31, Hans Verkuil wrote:
> (Changes since v1: fix the embarrassing bug where mmap_sem wasn't initialized)
>
> Commit f035eb4e976ef5a059e30bc91cfd310ff030a7d3 (videobuf2: fix lockdep warning)
> unfortunately removed the mmap_sem lock that is needed around the call to
> __qbuf_userptr. Amazingly nobody noticed this (especially me as the author)
> until Jan Kara pointed this out to me.
>
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Reported-by: Jan Kara <jack@xxxxxxx>
The patch looks good to me. You can add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> drivers/media/v4l2-core/videobuf2-core.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 5b808e2..a0ab6af 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -1591,6 +1591,7 @@ static void __enqueue_in_driver(struct vb2_buffer *vb)
> static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
> {
> struct vb2_queue *q = vb->vb2_queue;
> + struct rw_semaphore *mmap_sem;
> int ret;
>
> ret = __verify_length(vb, b);
> @@ -1627,7 +1628,10 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
> ret = __qbuf_mmap(vb, b);
> break;
> case V4L2_MEMORY_USERPTR:
> + mmap_sem = ¤t->mm->mmap_sem;
> + down_read(mmap_sem);
> ret = __qbuf_userptr(vb, b);
> + up_read(mmap_sem);
> break;
> case V4L2_MEMORY_DMABUF:
> ret = __qbuf_dmabuf(vb, b);
> --
> 2.0.1
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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