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[87.12.25.55]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac71961f8fbsm166142266b.107.2025.03.28.07.15.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Mar 2025 07:15:37 -0700 (PDT) From: Stefano Garzarella To: netdev@vger.kernel.org Cc: Michal Luczaj , Paolo Abeni , George Zhang , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Andy King , Stefano Garzarella , Eric Dumazet , "David S. Miller" , Jakub Kicinski , Dmitry Torokhov , Simon Horman , Luigi Leonardi Subject: [PATCH net] vsock: avoid timeout during connect() if the socket is closing Date: Fri, 28 Mar 2025 15:15:28 +0100 Message-ID: <20250328141528.420719-1-sgarzare@redhat.com> X-Mailer: git-send-email 2.49.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: kuba@kernel.org From: Stefano Garzarella When a peer attempts to establish a connection, vsock_connect() contains a loop that waits for the state to be TCP_ESTABLISHED. However, the other peer can be fast enough to accept the connection and close it immediately, thus moving the state to TCP_CLOSING. When this happens, the peer in the vsock_connect() is properly woken up, but since the state is not TCP_ESTABLISHED, it goes back to sleep until the timeout expires, returning -ETIMEDOUT. If the socket state is TCP_CLOSING, waiting for the timeout is pointless. vsock_connect() can return immediately without errors or delay since the connection actually happened. The socket will be in a closing state, but this is not an issue, and subsequent calls will fail as expected. We discovered this issue while developing a test that accepts and immediately closes connections to stress the transport switch between two connect() calls, where the first one was interrupted by a signal (see Closes link). Reported-by: Luigi Leonardi Closes: https://lore.kernel.org/virtualization/bq6hxrolno2vmtqwcvb5bljfpb7mvwb3kohrvaed6auz5vxrfv@ijmd2f3grobn/ Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Signed-off-by: Stefano Garzarella Acked-by: Paolo Abeni Tested-by: Luigi Leonardi Reviewed-by: Luigi Leonardi --- net/vmw_vsock/af_vsock.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 7e3db87ae433..fc6afbc8d680 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1551,7 +1551,11 @@ static int vsock_connect(struct socket *sock, struct sockaddr *addr, timeout = vsk->connect_timeout; prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); - while (sk->sk_state != TCP_ESTABLISHED && sk->sk_err == 0) { + /* If the socket is already closing or it is in an error state, there + * is no point in waiting. + */ + while (sk->sk_state != TCP_ESTABLISHED && + sk->sk_state != TCP_CLOSING && sk->sk_err == 0) { if (flags & O_NONBLOCK) { /* If we're not going to block, we schedule a timeout * function to generate a timeout on the connection