Re: [PATCH v2 2/2] virtio_ring: check desc == NULL when packed and indirect

[Jason Wang <jasowang@redhat.com>]

On Mon, Sep 27, 2021 at 6:54 PM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> In the case of packed, use indirect desc, since desc is allocated by
> kmalloc_array(), we should check whether its return value is NULL.
>
> This patch alloc desc inside virtqueue_add_packe(), if desc == NULL,
> fall back to not using indirect.
>
> Fixes: 1ce9e6055fa ("virtio_ring: introduce packed ring support")
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

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

> ---
>  drivers/virtio/virtio_ring.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 91a46c4da87d..62323c27bfe4 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1051,20 +1051,19 @@ static struct vring_packed_desc *alloc_indirect_packed(unsigned int total_sg,
>
>  static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
>                                          struct scatterlist *sgs[],
> +                                        struct vring_packed_desc *desc,
>                                          unsigned int total_sg,
>                                          unsigned int out_sgs,
>                                          unsigned int in_sgs,
>                                          void *data,
>                                          gfp_t gfp)
>  {
> -       struct vring_packed_desc *desc;
>         struct scatterlist *sg;
>         unsigned int i, n, err_idx;
>         u16 head, id;
>         dma_addr_t addr;
>
>         head = vq->packed.next_avail_idx;
> -       desc = alloc_indirect_packed(total_sg, gfp);
>
>         if (unlikely(vq->vq.num_free < 1)) {
>                 pr_debug("Can't add buf len 1 - avail = 0\n");
> @@ -1191,9 +1190,14 @@ static inline int virtqueue_add_packed(struct virtqueue *_vq,
>
>         BUG_ON(total_sg == 0);
>
> -       if (virtqueue_use_indirect(_vq, total_sg))
> -               return virtqueue_add_indirect_packed(vq, sgs, total_sg,
> -                               out_sgs, in_sgs, data, gfp);
> +       if (virtqueue_use_indirect(_vq, total_sg)) {
> +               desc = alloc_indirect_packed(total_sg, gfp);
> +               if (desc)
> +                       return virtqueue_add_indirect_packed(vq, sgs, desc,
> +                                                            total_sg,
> +                                                            out_sgs, in_sgs,
> +                                                            data, gfp);
> +       }
>
>         head = vq->packed.next_avail_idx;
>         avail_used_flags = vq->packed.avail_used_flags;
> --
> 2.31.0
>

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