SELinux: Only store the network interface's ifindex

Instead of storing the packet's network interface name store the ifindex. This
allows us to defer the need to lookup the net_device structure until the audit
record is generated meaning that in the majority of cases we never need to
bother with this at all.

Signed-off-by: Paul Moore <[e-mail]>
Signed-off-by: James Morris <[e-mail]>

security/selinux/avc.c

···
 						    "daddr", "dest");
 				break;
 			}
-			if (a->u.net.netif)
-				audit_log_format(ab, " netif=%s",
-					a->u.net.netif);
+			if (a->u.net.netif > 0) {
+				struct net_device *dev;
+
+				/* NOTE: we always use init's namespace */
+				dev = dev_get_by_index(&init_net,
+						       a->u.net.netif);
+				if (dev) {
+					audit_log_format(ab, " netif=%s",
+							 dev->name);
+					dev_put(dev);
+				}
+			}
 			break;
 		}
 	}

security/selinux/hooks.c

···
 		family = PF_INET;
 
 	AVC_AUDIT_DATA_INIT(&ad, NET);
-	ad.u.net.netif = skb->dev ? skb->dev->name : "[unknown]";
+	ad.u.net.netif = skb->iif;
 	ad.u.net.family = family;
 
 	err = selinux_parse_skb(skb, &ad, &addrp, &len, 1, NULL);
···
 	sksec = sk->sk_security;
 
 	AVC_AUDIT_DATA_INIT(&ad, NET);
-	ad.u.net.netif = dev->name;
+	ad.u.net.netif = dev->ifindex;
 	ad.u.net.family = family;
 
 	err = selinux_parse_skb(skb, &ad, &addrp, &len, 0, &proto);

security/selinux/include/avc.h

···
 			struct inode *inode;
 		} fs;
 		struct {
-			char *netif;
+			int netif;
 			struct sock *sk;
 			u16 family;
 			__be16 dport;