netdev - Re: [PATCH net] virtio/vsock: fix leak due to missing skb owner

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Date:   Tue, 28 Mar 2023 09:58:00 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Bobby Eshleman <bobby.eshleman@...edance.com>
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>, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH net] virtio/vsock: fix leak due to missing skb owner

On Mon, Mar 27, 2023 at 10:01:05PM +0000, Bobby Eshleman wrote:
>This patch sets the owner for the skb when being sent from a socket and
>so solves the leak caused when virtio_transport_purge_skbs() finds
>skb->sk is always NULL and therefore never matches it with the current
>socket. Setting the owner upon allocation fixes this.
>
>Fixes: 71dc9ec9ac7d ("virtio/vsock: replace virtio_vsock_pkt with sk_buff")
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>Reported-by: Cong Wang <xiyou.wangcong@...il.com>
>Link: https://lore.kernel.org/all/ZCCbATwov4U+GBUv@pop-os.localdomain/
>---
> net/vmw_vsock/virtio_transport_common.c | 3 +++
> 1 file changed, 3 insertions(+)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 957cdc01c8e8..2a2f0c1a9fbd 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -94,6 +94,9 @@ virtio_transport_alloc_skb(struct virtio_vsock_pkt_info *info,
> 					 info->op,
> 					 info->flags);
>
>+	if (info->vsk)
>+		skb_set_owner_w(skb, sk_vsock(info->vsk));
>+

Should we do the same also in virtio_transport_recv_pkt()?

The skb in that cases is allocated in drivers/vhost/vsock.c and
net/vmw_vsock/virtio_transport.c using directly
virtio_vsock_alloc_skb(), because we don't know in advance which socket
it belongs to.

Then in virtio_transport_recv_pkt() we look for the socket and queue it
up. This should also solve the problem in vsock_loopback.c where we move
skb from one socket to another.

Thanks,
Stefano