Date:   Fri, 10 Mar 2023 10:05:53 +0100
From:   Stefano Garzarella <sgarzare@redhat.com>
To:     Arseniy Krasnov <avkrasnov@sberdevices.ru>
Cc:     Stefan Hajnoczi <stefanha@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel@sberdevices.ru, oxffffaa@gmail.com
Subject: Re: [RFC PATCH v4 3/4] virtio/vsock: don't drop skbuff on copy
 failure
Message-ID: <20230310090553.mlvthrdpmehi5op5@sgarzare-redhat>
References: <1804d100-1652-d463-8627-da93cb61144e@sberdevices.ru>
 <e29e788a-51d7-f733-85a5-707044f54dd6@sberdevices.ru>
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Precedence: bulk

On Thu, Mar 09, 2023 at 11:28:01PM +0300, Arseniy Krasnov wrote:
>This returns behaviour of SOCK_STREAM read as before skbuff usage. When
>copying to user fails current skbuff won't be dropped, but returned to
>sockets's queue. Technically instead of 'skb_dequeue()', 'skb_peek()' is
>called and when skbuff becomes empty, it is removed from queue by
>'__skb_unlink()'.
>
>Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
>Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>

>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 9a411475e201..6564192e7f20 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -364,7 +364,7 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
>
> 	spin_lock_bh(&vvs->rx_lock);
> 	while (total < len && !skb_queue_empty(&vvs->rx_queue)) {
>-		skb = __skb_dequeue(&vvs->rx_queue);
>+		skb = skb_peek(&vvs->rx_queue);
>
> 		bytes = len - total;
> 		if (bytes > skb->len)
>@@ -388,9 +388,8 @@ virtio_transport_stream_do_dequeue(struct vsock_sock *vsk,
> 			u32 pkt_len = le32_to_cpu(virtio_vsock_hdr(skb)->len);
>
> 			virtio_transport_dec_rx_pkt(vvs, pkt_len);
>+			__skb_unlink(skb, &vvs->rx_queue);
> 			consume_skb(skb);
>-		} else {
>-			__skb_queue_head(&vvs->rx_queue, skb);
> 		}
> 	}
>
>-- 
>2.25.1
>