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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , George Zhang , Dmitry Torokhov , Andy King Cc: Nguyen Dinh Phi , syzbot+1b2c9c4a0f8708082678@syzkaller.appspotmail.com, Michal Luczaj , virtualization@lists.linux.dev, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v6 1/3] vsock: don't check the listener's sk_err in vsock_accept() Date: Fri, 14 Aug 2026 01:30:18 +0800 Message-ID: <20260813173024.2362935-2-phind.uet@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260813173024.2362935-1-phind.uet@gmail.com> References: <20260813173024.2362935-1-phind.uet@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Syzbot reported 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}) -> -1, EPROTO (self-connect) listen(r0, backlog) -> 0 r1 = socket(AF_VSOCK, SOCK_STREAM, 0) connect(r1, {VMADDR_CID_LOCAL, PORT}) -> 0 accept(r0) -> -1, EPROTO (stale sk_err) 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. For a non-blocking connect(), vsock_connect() may return -EINPROGRESS immediately, and vsock_connect_timeout() can later set sk->sk_err asynchronously. Since no vsock transport ever sets sk_err on a socket while it is in TCP_LISTEN state, checking it in vsock_accept() serves no purpose and only carries forward errors left behind by earlier, unrelated connection attempts on the same socket. Remove the checks so accept() no longer rejects valid incoming connections because of a stale error, which also avoids the resource leak described above. Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Reported-by: syzbot+1b2c9c4a0f8708082678@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1b2c9c4a0f8708082678 Suggested-by: Michal Luczaj Signed-off-by: Nguyen Dinh Phi --- net/vmw_vsock/af_vsock.c | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 622dbd046799..3cd5c3561be3 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1893,7 +1893,7 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, timeout = sock_rcvtimeo(listener, arg->flags & O_NONBLOCK); while ((connected = vsock_dequeue_accept(listener)) == NULL && - listener->sk_err == 0 && timeout != 0) { + timeout != 0) { prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE); release_sock(listener); timeout = schedule_timeout(timeout); @@ -1906,13 +1906,9 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, } } - if (listener->sk_err) { - err = -listener->sk_err; - } else if (!connected) { + if (!connected) { err = -EAGAIN; - } - - if (connected) { + } else { sk_acceptq_removed(listener); lock_sock_nested(connected, SINGLE_DEPTH_NESTING); -- 2.53.0