[NETFILTER]: Fix skb->nf_bridge lifetime issues

The bridge netfilter code simulates the NF_IP_PRE_ROUTING hook and skips
the real hook by registering with high priority and returning NF_STOP if
skb->nf_bridge is present and the BRNF_NF_BRIDGE_PREROUTING flag is not
set. The flag is only set during the simulated hook.

Because skb->nf_bridge is only freed when the packet is destroyed, the
packet will not only skip the first invocation of NF_IP_PRE_ROUTING, but
in the case of tunnel devices on top of the bridge also all further ones.
Forwarded packets from a bridge encapsulated by a tunnel device and sent
as locally outgoing packet will also still have the incorrect bridge
information from the input path attached.

We already have nf_reset calls on all RX/TX paths of tunnel devices,
so simply reset the nf_bridge field there too. As an added bonus,
the bridge information for locally delivered packets is now also freed
when the packet is queued to a socket.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -1351,16 +1351,6 @@ static inline void nf_conntrack_put_reasm(struct sk_buff *skb)
 		kfree_skb(skb);
 }
 #endif
-static inline void nf_reset(struct sk_buff *skb)
-{
-	nf_conntrack_put(skb->nfct);
-	skb->nfct = NULL;
-#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
-	nf_conntrack_put_reasm(skb->nfct_reasm);
-	skb->nfct_reasm = NULL;
-#endif
-}
-
 #ifdef CONFIG_BRIDGE_NETFILTER
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
@@ -1373,6 +1363,20 @@ static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
 		atomic_inc(&nf_bridge->use);
 }
 #endif /* CONFIG_BRIDGE_NETFILTER */
+static inline void nf_reset(struct sk_buff *skb)
+{
+	nf_conntrack_put(skb->nfct);
+	skb->nfct = NULL;
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+	nf_conntrack_put_reasm(skb->nfct_reasm);
+	skb->nfct_reasm = NULL;
+#endif
+#ifdef CONFIG_BRIDGE_NETFILTER
+	nf_bridge_put(skb->nf_bridge);
+	skb->nf_bridge = NULL;
+#endif
+}
+
 #else /* CONFIG_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb) {}
 #endif /* CONFIG_NETFILTER */

net/ipv4/netfilter/ipt_REJECT.c

@@ -154,10 +154,6 @@ static void send_reset(struct sk_buff *oldskb, int hook)
 	/* This packet will not be the same as the other: clear nf fields */
 	nf_reset(nskb);
 	nskb->nfmark = 0;
-#ifdef CONFIG_BRIDGE_NETFILTER
-	nf_bridge_put(nskb->nf_bridge);
-	nskb->nf_bridge = NULL;
-#endif
 
 	tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);