netdev - Re: [PATCH net v2 4/5] vsock: reset socket state when de-assigning the transport

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Message-ID: <fjx4nkajq3cnaxdbvs3dd2sxtc35tkqlqti3h44t3xuefclwar@havkg6jfisxu>
Date: Fri, 10 Jan 2025 12:25:09 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Luigi Leonardi <leonardi@...hat.com>
Cc: netdev@...r.kernel.org, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Wongi Lee <qwerty@...ori.io>, 
	Eugenio Pérez <eperezma@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>, 
	Eric Dumazet <edumazet@...gle.com>, kvm@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>, 
	Stefan Hajnoczi <stefanha@...hat.com>, Jason Wang <jasowang@...hat.com>, 
	Simon Horman <horms@...nel.org>, Hyunwoo Kim <v4bel@...ori.io>, Jakub Kicinski <kuba@...nel.org>, 
	Michal Luczaj <mhal@...x.co>, virtualization@...ts.linux.dev, 
	Bobby Eshleman <bobby.eshleman@...edance.com>, stable@...r.kernel.org
Subject: Re: [PATCH net v2 4/5] vsock: reset socket state when de-assigning
 the transport

On Fri, Jan 10, 2025 at 11:56:28AM +0100, Luigi Leonardi wrote:
>On Fri, Jan 10, 2025 at 09:35:10AM +0100, Stefano Garzarella wrote:
>>Transport's release() and destruct() are called when de-assigning the
>>vsock transport. These callbacks can touch some socket state like
>>sock flags, sk_state, and peer_shutdown.
>>
>>Since we are reassigning the socket to a new transport during
>>vsock_connect(), let's reset these fields to have a clean state with
>>the new transport.
>>
>>Fixes: c0cfa2d8a788 ("vsock: add multi-transports support")
>>Cc: stable@...r.kernel.org
>>Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>>---
>>net/vmw_vsock/af_vsock.c | 9 +++++++++
>>1 file changed, 9 insertions(+)
>>
>>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>index 5cf8109f672a..74d35a871644 100644
>>--- a/net/vmw_vsock/af_vsock.c
>>+++ b/net/vmw_vsock/af_vsock.c
>>@@ -491,6 +491,15 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>>		 */
>>		vsk->transport->release(vsk);
>>		vsock_deassign_transport(vsk);
>>+
>>+		/* transport's release() and destruct() can touch some socket
>>+		 * state, since we are reassigning the socket to a new transport
>>+		 * during vsock_connect(), let's reset these fields to have a
>>+		 * clean state.
>>+		 */
>>+		sock_reset_flag(sk, SOCK_DONE);
>>+		sk->sk_state = TCP_CLOSE;
>>+		vsk->peer_shutdown = 0;
>>	}
>>
>>	/* We increase the module refcnt to prevent the transport unloading
>>-- 
>>2.47.1
>>
>
>Hi Stefano,
>I spent some time investigating what would happen if the scheduled work
>ran before `virtio_transport_cancel_close_work`. IIUC that should do 
>no harm and all the fields are reset correctly.

Yep, after transport->destruct() call, the delayed work should have 
already finished or canceled.

>
>Thank you,
>Luigi
>
>Reviewed-by: Luigi Leonardi <leonardi@...hat.com>
>

Thanks for the review,
Stefano