selinux: do not report error on connect(AF_UNSPEC)

calling connect(AF_UNSPEC) on an already connected TCP socket is an
established way to disconnect() such socket. After commit 68741a8
("selinux: Fix ltp test connect-syscall failure") it no longer works
and, in the above scenario connect() fails with EAFNOSUPPORT.

Fix the above falling back to the generic/old code when the address family
is not AF_INET{4,6}, but leave the SCTP code path untouched, as it has
specific constraints.

Fixes: 68741a8 ("selinux: Fix ltp test connect-syscall failure")
Reported-by: Tom Deseyn <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
Reviewed-by: Marcelo Ricardo Leitner <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

security/selinux/hooks.c

@@ -4649,7 +4649,7 @@ static int selinux_socket_connect_helper(struct socket *sock,
 		struct lsm_network_audit net = {0,};
 		struct sockaddr_in *addr4 = NULL;
 		struct sockaddr_in6 *addr6 = NULL;
-		unsigned short snum;
+		unsigned short snum = 0;
 		u32 sid, perm;
 
 		/* sctp_connectx(3) calls via selinux_sctp_bind_connect()
@@ -4674,12 +4674,12 @@ static int selinux_socket_connect_helper(struct socket *sock,
 			break;
 		default:
 			/* Note that SCTP services expect -EINVAL, whereas
-			 * others expect -EAFNOSUPPORT.
+			 * others must handle this at the protocol level:
+			 * connect(AF_UNSPEC) on a connected socket is
+			 * a documented way disconnect the socket.
 			 */
 			if (sksec->sclass == SECCLASS_SCTP_SOCKET)
 				return -EINVAL;
-			else
-				return -EAFNOSUPPORT;
 		}
 
 		err = sel_netport_sid(sk->sk_protocol, snum, &sid);