linux-kernel - Re: [PATCH v2] vsock: notify server to shutdown when client has pending signal

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Message-ID: <20210621100222.jg7rajkjyzuao5h5@steredhat>
Date:   Mon, 21 Jun 2021 12:02:22 +0200
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     "Longpeng(Mike)" <longpeng2@...wei.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        arei.gonglei@...wei.com, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Norbert Slusarek <nslusarek@....net>,
        Andra Paraschiv <andraprs@...zon.com>,
        Colin Ian King <colin.king@...onical.com>,
        David Brazdil <dbrazdil@...gle.com>,
        Alexander Popov <alex.popov@...ux.com>,
        lixianming <lixianming5@...wei.com>
Subject: Re: [PATCH v2] vsock: notify server to shutdown when client has
 pending signal

On Mon, Jun 21, 2021 at 02:26:01PM +0800, Longpeng(Mike) wrote:
>The client's sk_state will be set to TCP_ESTABLISHED if the server
>replay the client's connect request.
>
>However, if the client has pending signal, its sk_state will be set
>to TCP_CLOSE without notify the server, so the server will hold the
>corrupt connection.
>
>            client                        server
>
>1. sk_state=TCP_SYN_SENT         |
>2. call ->connect()              |
>3. wait reply                    |
>                                 | 4. sk_state=TCP_ESTABLISHED
>                                 | 5. insert to connected list
>                                 | 6. reply to the client
>7. sk_state=TCP_ESTABLISHED      |
>8. insert to connected list      |
>9. *signal pending* <--------------------- the user kill client
>10. sk_state=TCP_CLOSE           |
>client is exiting...             |
>11. call ->release()             |
>     virtio_transport_close
>      if (!(sk->sk_state == TCP_ESTABLISHED ||
>	      sk->sk_state == TCP_CLOSING))
>		return true; *return at here, the server cannot notice the connection is corrupt*
>
>So the client should notify the peer in this case.
>
>Cc: David S. Miller <davem@...emloft.net>
>Cc: Jakub Kicinski <kuba@...nel.org>
>Cc: Jorgen Hansen <jhansen@...are.com>
>Cc: Norbert Slusarek <nslusarek@....net>
>Cc: Andra Paraschiv <andraprs@...zon.com>
>Cc: Colin Ian King <colin.king@...onical.com>
>Cc: David Brazdil <dbrazdil@...gle.com>
>Cc: Alexander Popov <alex.popov@...ux.com>
>Suggested-by: Stefano Garzarella <sgarzare@...hat.com>
>Link: https://lkml.org/lkml/2021/5/17/418
>Signed-off-by: lixianming <lixianming5@...wei.com>
>Signed-off-by: Longpeng(Mike) <longpeng2@...wei.com>
>---
> net/vmw_vsock/af_vsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 92a72f0..ae11311 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -1369,7 +1369,7 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr,
>
> 		if (signal_pending(current)) {
> 			err = sock_intr_errno(timeout);
>-			sk->sk_state = TCP_CLOSE;
>+			sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE;
> 			sock->state = SS_UNCONNECTED;
> 			vsock_transport_cancel_pkt(vsk);
> 			goto out_wait;
>-- 
>1.8.3.1
>

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