vsock: Do not allow binding to VMADDR_PORT_ANY

It is possible for a vsock to autobind to VMADDR_PORT_ANY. This can
cause a use-after-free when a connection is made to the bound socket.
The socket returned by accept() also has port VMADDR_PORT_ANY but is not
on the list of unbound sockets. Binding it will result in an extra
refcount decrement similar to the one fixed in fcdd2242c023 (vsock: Keep
the binding until socket destruction).

Modify the check in __vsock_bind_connectible() to also prevent binding
to VMADDR_PORT_ANY.

Fixes: d021c344051a ("VSOCK: Introduce VM Sockets")
Reported-by: Budimir Markovic <markovicbudimir@gmail.com>
Signed-off-by: Budimir Markovic <markovicbudimir@gmail.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20250807041811.678-1-markovicbudimir@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index ead6a3c14b87921e7de69fc94b4f921d84ab71a4..bebb355f3ffe2531e0c7e7ad69b639acee18d38d 100644 (file)
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -689,7 +689,8 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
                unsigned int i;
 
                for (i = 0; i < MAX_PORT_RETRIES; i++) {
-                       if (port <= LAST_RESERVED_PORT)
+                       if (port == VMADDR_PORT_ANY ||
+                           port <= LAST_RESERVED_PORT)
                                port = LAST_RESERVED_PORT + 1;
 
                        new_addr.svm_port = port++;