5.4-stable review patch. If anyone has any objections, please let me know.
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From: Michal Luczaj mhal@rbox.co
[ Upstream commit 002541ef650b742a198e4be363881439bb9d86b4 ]
During connect(), acting on a signal/timeout by disconnecting an already established socket leads to several issues:
1. connect() invoking vsock_transport_cancel_pkt() -> virtio_transport_purge_skbs() may race with sendmsg() invoking virtio_transport_get_credit(). This results in a permanently elevated `vvs->bytes_unsent`. Which, in turn, confuses the SOCK_LINGER handling.
2. connect() resetting a connected socket's state may race with socket being placed in a sockmap. A disconnected socket remaining in a sockmap breaks sockmap's assumptions. And gives rise to WARNs.
3. connect() transitioning SS_CONNECTED -> SS_UNCONNECTED allows for a transport change/drop after TCP_ESTABLISHED. Which poses a problem for any simultaneous sendmsg() or connect() and may result in a use-after-free/null-ptr-deref.
Do not disconnect socket on signal/timeout. Keep the logic for unconnected sockets: they don't linger, can't be placed in a sockmap, are rejected by sendmsg().
[1]: https://lore.kernel.org/netdev/e07fd95c-9a38-4eea-9638-133e38c2ec9b@rbox.co/ [2]: https://lore.kernel.org/netdev/20250317-vsock-trans-signal-race-v4-0-fc8837f... [3]: https://lore.kernel.org/netdev/60f1b7db-3099-4f6a-875e-af9f6ef194f6@rbox.co/
Fixes: d021c344051a ("VSOCK: Introduce VM Sockets") Signed-off-by: Michal Luczaj mhal@rbox.co Reviewed-by: Stefano Garzarella sgarzare@redhat.com Link: https://patch.msgid.link/20251119-vsock-interrupted-connect-v2-1-70734cf1233... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/vmw_vsock/af_vsock.c | 40 +++++++++++++++++++++++++++++++--------- 1 file changed, 31 insertions(+), 9 deletions(-)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index 831ca8da84813..2202a8ba2dfdc 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1235,18 +1235,40 @@ static int vsock_stream_connect(struct socket *sock, struct sockaddr *addr, timeout = schedule_timeout(timeout); lock_sock(sk);
- if (signal_pending(current)) { - err = sock_intr_errno(timeout); - sk->sk_state = sk->sk_state == TCP_ESTABLISHED ? TCP_CLOSING : TCP_CLOSE; - sock->state = SS_UNCONNECTED; - vsock_transport_cancel_pkt(vsk); - vsock_remove_connected(vsk); - goto out_wait; - } else if ((sk->sk_state != TCP_ESTABLISHED) && (timeout == 0)) { - err = -ETIMEDOUT; + /* Connection established. Whatever happens to socket once we + * release it, that's not connect()'s concern. No need to go + * into signal and timeout handling. Call it a day. + * + * Note that allowing to "reset" an already established socket + * here is racy and insecure. + */ + if (sk->sk_state == TCP_ESTABLISHED) + break; + + /* If connection was _not_ established and a signal/timeout came + * to be, we want the socket's state reset. User space may want + * to retry. + * + * sk_state != TCP_ESTABLISHED implies that socket is not on + * vsock_connected_table. We keep the binding and the transport + * assigned. + */ + if (signal_pending(current) || timeout == 0) { + err = timeout == 0 ? -ETIMEDOUT : sock_intr_errno(timeout); + + /* Listener might have already responded with + * VIRTIO_VSOCK_OP_RESPONSE. Its handling expects our + * sk_state == TCP_SYN_SENT, which hereby we break. + * In such case VIRTIO_VSOCK_OP_RST will follow. + */ sk->sk_state = TCP_CLOSE; sock->state = SS_UNCONNECTED; + + /* Try to cancel VIRTIO_VSOCK_OP_REQUEST skb sent out by + * transport->connect(). + */ vsock_transport_cancel_pkt(vsk); + goto out_wait; }