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

From: "Michael S. Tsirkin" <[email-masked]>
Date: Mon, 5 Jul 2021 14:08:22 -0400

On Mon, Jul 05, 2021 at 09:53:39PM +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")
> Fixes: a7c58146cf9a ("virtio_net: don't crash if virtqueue is broken.")

What does this have to do with it?

> Signed-off-by: Yunjian Wang <[email-masked]>
> ---
>  drivers/net/virtio_net.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b0b81458ca94..2b852578551e 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 +1763,9 @@ 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)
> +		return false;

and maybe dev_warn here. these things should not happen.

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