[media] videobuf2-core: take mmap_sem before calling __qbuf_userptr

(Changes since v2: dropped local variable as suggested by Laurent)

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>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 7e6aff673a5a..15b02f940ced 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1627,7 +1627,9 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
                 ret = __qbuf_mmap(vb, b);
                 break;
         case V4L2_MEMORY_USERPTR:
+                down_read(&current->mm->mmap_sem);
                 ret = __qbuf_userptr(vb, b);
+                up_read(&current->mm->mmap_sem);
                 break;
         case V4L2_MEMORY_DMABUF:
                 ret = __qbuf_dmabuf(vb, b);