Re: [PATCH 2/2] videobuf2-v4l2: Verify planes array in buffer dequeueing

Hans Verkuil
2016-04-06T14:44:39Z

On 04/06/2016 04:46 AM, Sakari Ailus wrote:
> When a buffer is being dequeued using VIDIOC_DQBUF IOCTL, the exact buffer
> which will be dequeued is not known until the buffer has been removed from
> the queue. The number of planes is specific to a buffer, not to the queue.
>
> This does lead to the situation where multi-plane buffers may be requested
> and queued with n planes, but VIDIOC_DQBUF IOCTL may be passed an argument
> struct with fewer planes.
>
> __fill_v4l2_buffer() however uses the number of planes from the dequeued
> videobuf2 buffer, overwriting kernel memory (the m.planes array allocated
> in video_usercopy() in v4l2-ioctl.c) if the user provided fewer
> planes than the dequeued buffer had. Oops!
>
> Fixes: b0e0e1f83de3 ("[media] media: videobuf2: Prepare to divide videobuf2")
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>

Acked-by: Hans Verkuil <hans.verkuil@cisco.com>

Thanks,

Hans

> ---
> drivers/media/v4l2-core/videobuf2-v4l2.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
> index 91f5521..8da7470 100644
> --- a/drivers/media/v4l2-core/videobuf2-v4l2.c
> +++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
> @@ -74,6 +74,11 @@ static int __verify_planes_array(struct vb2_buffer *vb, const struct v4l2_buffer
> return 0;
> }
>
> +static int __verify_planes_array_core(struct vb2_buffer *vb, const void *pb)
> +{
> + return __verify_planes_array(vb, pb);
> +}
> +
> /**
> * __verify_length() - Verify that the bytesused value for each plane fits in
> * the plane length and that the data offset doesn't exceed the bytesused value.
> @@ -437,6 +442,7 @@ static int __fill_vb2_buffer(struct vb2_buffer *vb,
> }
>
> static const struct vb2_buf_ops v4l2_buf_ops = {
> + .verify_planes_array = __verify_planes_array_core,
> .fill_user_buffer = __fill_v4l2_buffer,
> .fill_vb2_buffer = __fill_vb2_buffer,
> .copy_timestamp = __copy_timestamp,
>