* [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr
@ 2014-08-22 23:31 Hans Verkuil
2014-08-23 17:15 ` Laurent Pinchart
2014-08-26 9:09 ` Jan Kara
0 siblings, 2 replies; 3+ messages in thread
From: Hans Verkuil @ 2014-08-22 23:31 UTC (permalink / raw)
To: LMML; +Cc: Jan Kara, Laurent Pinchart, m.szyprowski, pawel
(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@cisco.com>
Reported-by: Jan Kara <jack@suse.cz>
---
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr
2014-08-22 23:31 [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr Hans Verkuil
@ 2014-08-23 17:15 ` Laurent Pinchart
2014-08-26 9:09 ` Jan Kara
1 sibling, 0 replies; 3+ messages in thread
From: Laurent Pinchart @ 2014-08-23 17:15 UTC (permalink / raw)
To: Hans Verkuil; +Cc: LMML, Jan Kara, m.szyprowski, pawel
Hi Hans,
Thank you for the patch.
On Friday 22 August 2014 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@cisco.com>
> Reported-by: Jan Kara <jack@suse.cz>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
but please see below for one small comment.
> ---
> 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;
Do we really need the local variable ?
> 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);
--
Regards,
Laurent Pinchart
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr
2014-08-22 23:31 [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr Hans Verkuil
2014-08-23 17:15 ` Laurent Pinchart
@ 2014-08-26 9:09 ` Jan Kara
1 sibling, 0 replies; 3+ messages in thread
From: Jan Kara @ 2014-08-26 9:09 UTC (permalink / raw)
To: Hans Verkuil; +Cc: LMML, Jan Kara, Laurent Pinchart, m.szyprowski, pawel
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@cisco.com>
> Reported-by: Jan Kara <jack@suse.cz>
The patch looks good to me. You can add:
Reviewed-by: Jan Kara <jack@suse.cz>
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@suse.cz>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2014-08-26 9:09 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2014-08-22 23:31 [PATCHv2] videobuf2-core: take mmap_sem before calling __qbuf_userptr Hans Verkuil
2014-08-23 17:15 ` Laurent Pinchart
2014-08-26 9:09 ` Jan Kara
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