netdev - Re: [PATCH net] virtio/vsock: fix sock refcnt bug on owner set failure

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Date: Thu, 1 Jun 2023 09:58:47 +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
Subject: Re: [PATCH net] virtio/vsock: fix sock refcnt bug on owner set
 failure

On Wed, May 31, 2023 at 07:47:32PM +0000, Bobby Eshleman wrote:
>Previous to setting the owner the socket is found via
>vsock_find_connected_socket(), which returns sk after a call to
>sock_hold().
>
>If setting the owner fails, then sock_put() needs to be called.
>
>Fixes: f9d2b1e146e0 ("virtio/vsock: fix leaks due to missing skb owner")
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>---
> net/vmw_vsock/virtio_transport_common.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index b769fc258931..f01cd6adc5cb 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -1343,6 +1343,7 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
>
> 	if (!skb_set_owner_sk_safe(skb, sk)) {
> 		WARN_ONCE(1, "receiving vsock socket has sk_refcnt == 0\n");
>+		sock_put(sk);

Did you have any warning, issue here?

IIUC skb_set_owner_sk_safe() can return false only if the ref counter
is 0, so calling a sock_put() on it should have no effect except to
produce a warning.

Thanks,
Stefano