Virtio/PM events are serviced by virtio_vsock_reset_sock(), which resets
each connected socket. The reset is done under vsock_table_lock but without
taking lock_sock(), so from the point of view of vsock_connect() -
locklessly. The same pattern exists in VMCI's
vmci_transport_handle_detach() and vhost's vhost_vsock_reset_orphans().
The complexity of connect() comes from the fact that:
1. the virtio transport can be reassigned, so the old transport must be
safely released;
2. a failed connect can be followed by a retry, so the socket must be
reverted to a sensible state.
Both cases apply only as long as the socket has not yet established a
connection.
While connect() waits for TCP_SYN_SENT -> TCP_ESTABLISHED, other
transitions can also occur:
TCP_SYN_SENT -> TCP_CLOSE on connection failure, timeout or signal
TCP_SYN_SENT -> TCP_ESTABLISHED -> TCP_CLOSING on VIRTIO_VSOCK_OP_RST
TCP_SYN_SENT -> TCP_ESTABLISHED -> [TCP_CLOSING ->] TCP_CLOSE on event
This further complicates connect(). Rather than making every event handler
drop the socket from connected_table or adapting connect() to handle more
transitions (while missing proper locking), use vsk->peer_shutdown as a
poison flag. Whatever state an event leaves the socket in, the flag bricks
it and prevents suspicious transport reassignments or TCP_SYN_SENT
retransmissions.
Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
Signed-off-by: Michal Luczaj <[email protected]>
---
net/vmw_vsock/af_vsock.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index adf3f018347e..972952d04a81 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1743,6 +1743,12 @@ static int vsock_connect(struct socket *sock, struct
sockaddr_unsized *addr,
goto out;
}
+ /* Virtio/PM events are serviced locklessly. */
+ if (READ_ONCE(vsk->peer_shutdown)) {
+ err = -ECONNRESET;
+ goto out;
+ }
+
/* Set the remote address that we are connecting to. */
memcpy(&vsk->remote_addr, remote_addr,
sizeof(vsk->remote_addr));
--
2.55.0
