linux-kernel - Re: [PATCH] virtio_ring: mark ring unused on error

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Message-ID: <CACGkMEtitniJqz0gMp4YY=sf_Nb0v8Z-xXyF9P_rh=+58Sn6Yg@mail.gmail.com>
Date:   Fri, 7 Jan 2022 10:24:50 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        virtualization <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH] virtio_ring: mark ring unused on error

On Thu, Jan 6, 2022 at 9:00 PM Michael S. Tsirkin <mst@...hat.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@...ux.alibaba.com>
> Cc: Jiasheng Jiang <jiasheng@...as.ac.cn>
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

Acked-by: Jason Wang <jasowang@...hat.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
>