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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Andy King , Dmitry Torokhov , George Zhang Cc: Nguyen Dinh Phi , syzbot+1b2c9c4a0f8708082678@syzkaller.appspotmail.com, virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] vsock: use sock_error() to consume sk_err after a Date: Mon, 27 Jul 2026 15:13:02 +0800 Message-ID: <20260727071305.45826-1-phind.uet@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Nguyen Dinh Phi Syzbot report an issue which can be reproduced with these steps: r0 = socket(AF_VSOCK, SOCK_STREAM, 0) bind(r0, {VMADDR_CID_ANY, PORT}) connect(r0, {VMADDR_CID_LOCAL, PORT}) listen(r0, backlog) r1 = socket(AF_VSOCK, SOCK_STREAM, 0) connect(r1, {VMADDR_CID_LOCAL, PORT}) connect(r0 -> self) -> -1, EPROTO listen(r0) -> 0 connect(r1 -> r0) -> 0 accept(r0) -> -1, EPROTO Basically, it creates a socket (r0) and triggers a self-connect after binding it. This self-connect fails with EPROTO because it loops back to r0 while the socket is still in the TCP_SYN_SENT state, causing it to be incorrectly dispatched to the connecting-client path. The unexpected packet type encountered there sets sk_err to EPROTO. After that, it invokes a listen() call on the same socket. This listen() call succeeds because the kernel's listening path never inspects or clears sk_err. Then, a new socket (r1) is created as a normal client and connects to r0. However, vsock_accept() rejects this incoming connection because the listener's sk_err still holds the EPROTO error from the earlier failed self-connect. This rejection causes the child socket created for r1's connection to never be freed on virtio or hyperv transports; only the VMCI transport implements pending_work to revisit and clean up a rejected socket Fix the issue by using sock_error() to read the sk_err to prevent the rejection branch from occurring in this scenario. sock_error() atomically reads and clears sk_err, ensuring the error is consumed when vsock_connect() returns and cannot affect subsequent operations on the same socket. This matches the established pattern used by other protocol connect() implementations in the network stack like __inet_stream_connect(), tipc_wait_for_connect()... Reported-by: syzbot+1b2c9c4a0f8708082678@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1b2c9c4a0f8708082678 Fixes: d021c344051af ("VSOCK: Introduce VM Sockets") Signed-off-by: Nguyen Dinh Phi --- V2: Add reproducer steps to commit message. net/vmw_vsock/af_vsock.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 622dbd046799..43eddc33ed12 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1847,14 +1847,11 @@ static int vsock_connect(struct socket *sock, struct sockaddr_unsized *addr, prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); } - if (sk->sk_err) { - err = -sk->sk_err; + err = sock_error(sk); + if (err) { sk->sk_state = TCP_CLOSE; sock->state = SS_UNCONNECTED; - } else { - err = 0; } - out_wait: finish_wait(sk_sleep(sk), &wait); out: -- 2.53.0