A recently added error path does not mark ring unused when exiting on
OOM, which will lead to BUG on the next entry in debug builds.

TODO: refactor code so we have START_USE and END_USE in the same function.

Fixes: fc6d70f40b3d ("virtio_ring: check desc == NULL when using indirect with packed")
Cc: "Xuan Zhuo" <xuanzhuo@linux.alibaba.com>
Cc: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_ring.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 028b05d44546..962f1477b1fa 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -1197,8 +1197,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
 	if (virtqueue_use_indirect(_vq, total_sg)) {
 		err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
 						    in_sgs, data, gfp);
-		if (err != -ENOMEM)
+		if (err != -ENOMEM) {
+			END_USE(vq);
 			return err;
+		}
 
 		/* fall back on direct */
 	}
-- 
MST

On Thu, Jan 6, 2022 at 9:00 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> A recently added error path does not mark ring unused when exiting on
> OOM, which will lead to BUG on the next entry in debug builds.
>
> TODO: refactor code so we have START_USE and END_USE in the same function.
>
> Fixes: fc6d70f40b3d ("virtio_ring: check desc == NULL when using indirect with packed")
> Cc: "Xuan Zhuo" <xuanzhuo@linux.alibaba.com>
> Cc: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Acked-by: Jason Wang <jasowang@redhat.com>

> ---
>  drivers/virtio/virtio_ring.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 028b05d44546..962f1477b1fa 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1197,8 +1197,10 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>         if (virtqueue_use_indirect(_vq, total_sg)) {
>                 err = virtqueue_add_indirect_packed(vq, sgs, total_sg, out_sgs,
>                                                     in_sgs, data, gfp);
> -               if (err != -ENOMEM)
> +               if (err != -ENOMEM) {
> +                       END_USE(vq);
>                         return err;
> +               }
>
>                 /* fall back on direct */
>         }
> --
> MST
>