netdev - Re: [RFC PATCH v4 3/4] virtio/vsock: don't drop skbuff on copy failure

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Message-ID: <20230310090553.mlvthrdpmehi5op5@sgarzare-redhat>
Date:   Fri, 10 Mar 2023 10:05:53 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <avkrasnov@...rdevices.ru>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Bobby Eshleman <bobby.eshleman@...edance.com>,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...rdevices.ru, oxffffaa@...il.com
Subject: Re: [RFC PATCH v4 3/4] virtio/vsock: don't drop skbuff on copy
 failure

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@...rdevices.ru>
>---
> net/vmw_vsock/virtio_transport_common.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)

Reviewed-by: Stefano Garzarella <sgarzare@...hat.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
>