selinux: avoid uninitialized variable warning

clang correctly points out a code path that would lead
to an uninitialized variable use:

security/selinux/netlabel.c:310:6: error: variable 'addr' is used uninitialized whenever 'if' condition is false
      [-Werror,-Wsometimes-uninitialized]
        if (ip_hdr(skb)->version == 4) {
            ^~~~~~~~~~~~~~~~~~~~~~~~~
security/selinux/netlabel.c:322:40: note: uninitialized use occurs here
        rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);
                                              ^~~~
security/selinux/netlabel.c:310:2: note: remove the 'if' if its condition is always true
        if (ip_hdr(skb)->version == 4) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
security/selinux/netlabel.c:291:23: note: initialize the variable 'addr' to silence this warning
        struct sockaddr *addr;
                             ^
                              = NULL

This is probably harmless since we should not see ipv6 packets
of CONFIG_IPV6 is disabled, but it's better to rearrange the code
so this cannot happen.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[PM: removed old patchwork link, fixed checkpatch.pl style errors]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/netlabel.c

@@ -288,11 +288,8 @@ int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
 	int rc;
 	struct netlbl_lsm_secattr secattr;
 	struct sk_security_struct *sksec = ep->base.sk->sk_security;
-	struct sockaddr *addr;
 	struct sockaddr_in addr4;
-#if IS_ENABLED(CONFIG_IPV6)
 	struct sockaddr_in6 addr6;
-#endif
 
 	if (ep->base.sk->sk_family != PF_INET &&
 				ep->base.sk->sk_family != PF_INET6)
@@ -310,16 +307,15 @@ int selinux_netlbl_sctp_assoc_request(struct sctp_endpoint *ep,
 	if (ip_hdr(skb)->version == 4) {
 		addr4.sin_family = AF_INET;
 		addr4.sin_addr.s_addr = ip_hdr(skb)->saddr;
-		addr = (struct sockaddr *)&addr4;
-#if IS_ENABLED(CONFIG_IPV6)
-	} else {
+		rc = netlbl_conn_setattr(ep->base.sk, (void *)&addr4, &secattr);
+	} else if (IS_ENABLED(CONFIG_IPV6) && ip_hdr(skb)->version == 6) {
 		addr6.sin6_family = AF_INET6;
 		addr6.sin6_addr = ipv6_hdr(skb)->saddr;
-		addr = (struct sockaddr *)&addr6;
-#endif
+		rc = netlbl_conn_setattr(ep->base.sk, (void *)&addr6, &secattr);
+	} else {
+		rc = -EAFNOSUPPORT;
 	}
 
-	rc = netlbl_conn_setattr(ep->base.sk, addr, &secattr);
 	if (rc == 0)
 		sksec->nlbl_state = NLBL_LABELED;