Re: [PATCH v4] virtio_blk: Fix an SG_IO regression

[Christoph Hellwig <hch@lst.de>]

On Thu, Oct 26, 2017 at 12:10:15PM +0200, Bart Van Assche wrote:
> Avoid that submitting an SG_IO ioctl triggers a kernel oops that
> is preceded by:
> 
> usercopy: kernel memory overwrite attempt detected to (null) (<null>) (6 bytes)
> kernel BUG at mm/usercopy.c:72!
> 
> Reported-by: Dann Frazier <dann.frazier@canonical.com>
> Fixes: commit ca18d6f769d2 ("block: Make most scsi_req_init() calls implicit")
> Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Dann Frazier <dann.frazier@canonical.com>
> Cc: <stable@vger.kernel.org> # v4.13
> ---
>  drivers/block/virtio_blk.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 34e17ee799be..e477d4a5181e 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -593,10 +593,20 @@ static int virtblk_map_queues(struct blk_mq_tag_set *set)
>  	return blk_mq_virtio_map_queues(set, vblk->vdev, 0);
>  }
>  
> +static void virtblk_initialize_rq(struct request *req)
> +{
> +	struct virtblk_req *vbr = blk_mq_rq_to_pdu(req);
> +
> +#ifdef CONFIG_VIRTIO_BLK_SCSI
> +	scsi_req_init(&vbr->sreq);
> +#endif

How about only defininig the initialize_rq method and implementation
if CONFIG_VIRTIO_BLK_SCSI is set?

Else looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>