Subject: Re: [PATCH net-next] virtio_net: check virtqueue_add_sgs() return value

From: "Michael S. Tsirkin" <[email-masked]>
Date: Fri, 9 Jul 2021 07:17:48 -0400

On Fri, Jul 09, 2021 at 06:21:31PM +0800, wangyunjian wrote:
> From: Yunjian Wang <[email-masked]>
> 
> As virtqueue_add_sgs() can fail, we should check the return value.
> 
> Addresses-Coverity-ID: 1464439 ("Unchecked return value")
> Signed-off-by: Yunjian Wang <[email-masked]>
> ---
> v2:
>   add warn log and remove fix tag
> ---
>  drivers/net/virtio_net.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b0b81458ca94..30a0ca2fef1a 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1743,6 +1743,7 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  {
>  	struct scatterlist *sgs[4], hdr, stat;
>  	unsigned out_num = 0, tmp;
> +	int ret;
>  
>  	/* Caller should know better */
>  	BUG_ON(!virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ));
> @@ -1762,7 +1763,12 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
>  	sgs[out_num] = &stat;
>  
>  	BUG_ON(out_num + 1 > ARRAY_SIZE(sgs));
> -	virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
> +	ret = virtqueue_add_sgs(vi->cvq, sgs, out_num, 1, vi, GFP_ATOMIC);
> +	if (ret < 0) {
> +		dev_warn(&vi->vdev->dev,
> +			 "Failed to add sgs for vq: %d\n.", ret);

That's not too clear. Pls make it clear that it's the command vq
that failed.

> +		return false;
> +	}
>  
>  	if (unlikely(!virtqueue_kick(vi->cvq)))
>  		return vi->ctrl->status == VIRTIO_NET_OK;
> -- 
> 2.23.0