Smack: Consolidate uses of secmark into a function

Add a function smack_from_skb() that returns the Smack label
identified by a network secmark. Replace the explicit uses of
the secmark with this function.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

security/smack/smack_lsm.c

@@ -3810,6 +3810,20 @@ static int smk_skb_to_addr_ipv6(struct sk_buff *skb, struct sockaddr_in6 *sip)
 }
 #endif /* CONFIG_IPV6 */
 
+/**
+ * smack_from_skb - Smack data from the secmark in an skb
+ * @skb: packet
+ *
+ * Returns smack_known of the secmark or NULL if that won't work.
+ */
+static struct smack_known *smack_from_skb(struct sk_buff *skb)
+{
+	if (skb == NULL || skb->secmark == 0)
+		return NULL;
+
+	return smack_from_secid(skb->secmark);
+}
+
 /**
  * smack_socket_sock_rcv_skb - Smack packet delivery access check
  * @sk: socket
@@ -3838,17 +3852,14 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 
 	switch (family) {
 	case PF_INET:
-#ifdef CONFIG_SECURITY_SMACK_NETFILTER
 		/*
 		 * If there is a secmark use it rather than the CIPSO label.
 		 * If there is no secmark fall back to CIPSO.
 		 * The secmark is assumed to reflect policy better.
 		 */
-		if (skb && skb->secmark != 0) {
-			skp = smack_from_secid(skb->secmark);
+		skp = smack_from_skb(skb);
+		if (skp)
 			goto access_check;
-		}
-#endif /* CONFIG_SECURITY_SMACK_NETFILTER */
 		/*
 		 * Translate what netlabel gave us.
 		 */
@@ -3862,9 +3873,8 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 
 		netlbl_secattr_destroy(&secattr);
 
-#ifdef CONFIG_SECURITY_SMACK_NETFILTER
 access_check:
-#endif
+
 #ifdef CONFIG_AUDIT
 		smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);
 		ad.a.u.net->family = family;
@@ -3890,16 +3900,14 @@ static int smack_socket_sock_rcv_skb(struct sock *sk, struct sk_buff *skb)
 		    proto != IPPROTO_TCP && proto != IPPROTO_DCCP)
 			break;
 #ifdef SMACK_IPV6_SECMARK_LABELING
-		if (skb && skb->secmark != 0)
-			skp = smack_from_secid(skb->secmark);
-		else if (smk_ipv6_localhost(&sadd))
-			break;
-		else
+		skp = smack_from_skb(skb);
+		if (skp == NULL) {
+			if (smk_ipv6_localhost(&sadd))
+				break;
 			skp = smack_ipv6host_label(&sadd);
-		if (skp == NULL)
-			skp = smack_net_ambient;
-		if (skb == NULL)
-			break;
+			if (skp == NULL)
+				skp = smack_net_ambient;
+		}
 #ifdef CONFIG_AUDIT
 		smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);
 		ad.a.u.net->family = family;
@@ -3995,11 +4003,11 @@ static int smack_socket_getpeersec_dgram(struct socket *sock,
 		s = ssp->smk_out->smk_secid;
 		break;
 	case PF_INET:
-#ifdef CONFIG_SECURITY_SMACK_NETFILTER
-		s = skb->secmark;
-		if (s != 0)
+		skp = smack_from_skb(skb);
+		if (skp) {
+			s = skp->smk_secid;
 			break;
-#endif
+		}
 		/*
 		 * Translate what netlabel gave us.
 		 */
@@ -4015,7 +4023,9 @@ static int smack_socket_getpeersec_dgram(struct socket *sock,
 		break;
 	case PF_INET6:
 #ifdef SMACK_IPV6_SECMARK_LABELING
-		s = skb->secmark;
+		skp = smack_from_skb(skb);
+		if (skp)
+			s = skp->smk_secid;
 #endif
 		break;
 	}
@@ -4087,17 +4097,14 @@ static int smack_inet_conn_request(struct sock *sk, struct sk_buff *skb,
 	}
 #endif /* CONFIG_IPV6 */
 
-#ifdef CONFIG_SECURITY_SMACK_NETFILTER
 	/*
 	 * If there is a secmark use it rather than the CIPSO label.
 	 * If there is no secmark fall back to CIPSO.
 	 * The secmark is assumed to reflect policy better.
 	 */
-	if (skb && skb->secmark != 0) {
-		skp = smack_from_secid(skb->secmark);
+	skp = smack_from_skb(skb);
+	if (skp)
 		goto access_check;
-	}
-#endif /* CONFIG_SECURITY_SMACK_NETFILTER */
 
 	netlbl_secattr_init(&secattr);
 	rc = netlbl_skbuff_getattr(skb, family, &secattr);
@@ -4107,9 +4114,7 @@ static int smack_inet_conn_request(struct sock *sk, struct sk_buff *skb,
 		skp = &smack_known_huh;
 	netlbl_secattr_destroy(&secattr);
 
-#ifdef CONFIG_SECURITY_SMACK_NETFILTER
 access_check:
-#endif
 
 #ifdef CONFIG_AUDIT
 	smk_ad_init_net(&ad, __func__, LSM_AUDIT_DATA_NET, &net);