netdev - Re: [PATCH net v2 2/2] virtio_net: free xdp shinfo frags when build_skb_from_xdp

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Date:   Wed, 15 Mar 2023 10:14:34 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, <netdev@...r.kernel.org>
CC:     "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Heng Qi <hengqi@...ux.alibaba.com>,
        <virtualization@...ts.linux-foundation.org>, <bpf@...r.kernel.org>
Subject: Re: [PATCH net v2 2/2] virtio_net: free xdp shinfo frags when
 build_skb_from_xdp_buff() fails

On 2023/3/15 9:52, Xuan Zhuo wrote:
> build_skb_from_xdp_buff() may return NULL, in this case
> we need to free the frags of xdp shinfo.
> 
> Fixes: fab89bafa95b ("virtio-net: support multi-buffer xdp")
> Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  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 8ecf7a341d54..2396c28c0122 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1273,9 +1273,12 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
>  
>  		switch (act) {
>  		case XDP_PASS:
> +			head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
> +			if (unlikely(!head_skb))
> +				goto err_xdp_frags;

LGTM.
Reviewed-by: Yunsheng Lin <linyunsheng@...wei.com>

Note, "stats->drops++; dev_kfree_skb(head_skb);" is also done for the above case,
I assume it is ok as other "goto err_xdp_frags" case also do that.

> +
>  			if (unlikely(xdp_page != page))
>  				put_page(page);
> -			head_skb = build_skb_from_xdp_buff(dev, vi, &xdp, xdp_frags_truesz);
>  			rcu_read_unlock();
>  			return head_skb;
>  		case XDP_TX:
>