vsock: use ns_capable_noaudit() on socket create

During __vsock_create() CAP_NET_ADMIN is used to determine if the
vsock_sock->trusted should be set to true. This value is used later
for determing if a remote connection should be allowed to connect
to a restricted VM. Unfortunately, if the caller doesn't have
CAP_NET_ADMIN, an audit message such as an selinux denial is
generated even if the caller does not want a trusted socket.

Logging errors on success is confusing. To avoid this, switch the
capable(CAP_NET_ADMIN) check to the noaudit version.
Reported-by: Roman Kiryanov <rkir@google.com>
https://android-review.googlesource.com/c/device/generic/goldfish/+/1468545/Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Reviewed-by: James Morris <jamorris@linux.microsoft.com>
Link: https://lore.kernel.org/r/20201023143757.377574-1-jeffv@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/vmw_vsock/af_vsock.c

@@ -739,7 +739,7 @@ static struct sock *__vsock_create(struct net *net,
 		vsk->buffer_min_size = psk->buffer_min_size;
 		vsk->buffer_max_size = psk->buffer_max_size;
 	} else {
-		vsk->trusted = capable(CAP_NET_ADMIN);
+		vsk->trusted = ns_capable_noaudit(&init_user_ns, CAP_NET_ADMIN);
 		vsk->owner = get_current_cred();
 		vsk->connect_timeout = VSOCK_DEFAULT_CONNECT_TIMEOUT;
 		vsk->buffer_size = VSOCK_DEFAULT_BUFFER_SIZE;