[BRIDGE]: netfilter handle RCU during removal

Bridge netfilter code needs to handle the case where device is
removed from bridge while packet in process. In these cases the
bridge_parent can become null while processing.

This should fix: http://bugzilla.kernel.org/show_bug.cgi?id=5803

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 38 insertions, 15 deletions

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 7cac3fb9f809..b5018166b0e5 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -51,9 +51,6 @@
 #define store_orig_dstaddr(skb)  (skb_origaddr(skb) = (skb)->nh.iph->daddr)
 #define dnat_took_place(skb)     (skb_origaddr(skb) != (skb)->nh.iph->daddr)
 
-#define has_bridge_parent(device)       ((device)->br_port != NULL)
-#define bridge_parent(device)           ((device)->br_port->br->dev)
-
 #ifdef CONFIG_SYSCTL
 static struct ctl_table_header *brnf_sysctl_header;
 static int brnf_call_iptables = 1;
@@ -98,6 +95,12 @@ static struct rtable __fake_rtable = {
         .rt_flags       = 0,
 };
 
+static inline struct net_device *bridge_parent(const struct net_device *dev)
+{
+        struct net_bridge_port *port = rcu_dereference(dev->br_port);
+
+        return port ? port->br->dev : NULL;
+}
 
 /* PF_BRIDGE/PRE_ROUTING *********************************************/
 /* Undo the changes made for ip6tables PREROUTING and continue the
@@ -189,11 +192,15 @@ static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
         skb->nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
 
         skb->dev = bridge_parent(skb->dev);
-        if (skb->protocol == __constant_htons(ETH_P_8021Q)) {
-                skb_pull(skb, VLAN_HLEN);
-                skb->nh.raw += VLAN_HLEN;
+        if (!skb->dev)
+                kfree_skb(skb);
+        else {
+                if (skb->protocol == __constant_htons(ETH_P_8021Q)) {
+                        skb_pull(skb, VLAN_HLEN);
+                        skb->nh.raw += VLAN_HLEN;
+                }
+                skb->dst->output(skb);
         }
-        skb->dst->output(skb);
         return 0;
 }
 
@@ -270,7 +277,7 @@ bridged_dnat:
 }
 
 /* Some common code for IPv4/IPv6 */
-static void setup_pre_routing(struct sk_buff *skb)
+static struct net_device *setup_pre_routing(struct sk_buff *skb)
 {
         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
 
@@ -282,6 +289,8 @@ static void setup_pre_routing(struct sk_buff *skb)
         nf_bridge->mask |= BRNF_NF_BRIDGE_PREROUTING;
         nf_bridge->physindev = skb->dev;
         skb->dev = bridge_parent(skb->dev);
+
+        return skb->dev;
 }
 
 /* We only check the length. A bridge shouldn't do any hop-by-hop stuff anyway */
@@ -376,7 +385,8 @@ static unsigned int br_nf_pre_routing_ipv6(unsigned int hook,
         nf_bridge_put(skb->nf_bridge);
         if ((nf_bridge = nf_bridge_alloc(skb)) == NULL)
                 return NF_DROP;
-        setup_pre_routing(skb);
+        if (!setup_pre_routing(skb))
+                return NF_DROP;
 
         NF_HOOK(PF_INET6, NF_IP6_PRE_ROUTING, skb, skb->dev, NULL,
                 br_nf_pre_routing_finish_ipv6);
@@ -465,7 +475,8 @@ static unsigned int br_nf_pre_routing(unsigned int hook, struct sk_buff **pskb,
         nf_bridge_put(skb->nf_bridge);
         if ((nf_bridge = nf_bridge_alloc(skb)) == NULL)
                 return NF_DROP;
-        setup_pre_routing(skb);
+        if (!setup_pre_routing(skb))
+                return NF_DROP;
         store_orig_dstaddr(skb);
 
         NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, skb->dev, NULL,
@@ -539,11 +550,16 @@ static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff **pskb,
         struct sk_buff *skb = *pskb;
         struct nf_bridge_info *nf_bridge;
         struct vlan_ethhdr *hdr = vlan_eth_hdr(skb);
+        struct net_device *parent;
         int pf;
 
         if (!skb->nf_bridge)
                 return NF_ACCEPT;
 
+        parent = bridge_parent(out);
+        if (!parent)
+                return NF_DROP;
+
         if (skb->protocol == __constant_htons(ETH_P_IP) || IS_VLAN_IP)
                 pf = PF_INET;
         else
@@ -564,8 +580,8 @@ static unsigned int br_nf_forward_ip(unsigned int hook, struct sk_buff **pskb,
         nf_bridge->mask |= BRNF_BRIDGED;
         nf_bridge->physoutdev = skb->dev;
 
-        NF_HOOK(pf, NF_IP_FORWARD, skb, bridge_parent(in),
-                bridge_parent(out), br_nf_forward_finish);
+        NF_HOOK(pf, NF_IP_FORWARD, skb, bridge_parent(in), parent,
+                br_nf_forward_finish);
 
         return NF_STOLEN;
 }
@@ -688,6 +704,8 @@ static unsigned int br_nf_local_out(unsigned int hook, struct sk_buff **pskb,
                 goto out;
         }
         realoutdev = bridge_parent(skb->dev);
+        if (!realoutdev)
+                return NF_DROP;
 
 #if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
         /* iptables should match -o br0.x */
@@ -701,9 +719,11 @@ static unsigned int br_nf_local_out(unsigned int hook, struct sk_buff **pskb,
         /* IP forwarded traffic has a physindev, locally
          * generated traffic hasn't. */
         if (realindev != NULL) {
-                if (!(nf_bridge->mask & BRNF_DONT_TAKE_PARENT) &&
-                    has_bridge_parent(realindev))
-                        realindev = bridge_parent(realindev);
+                if (!(nf_bridge->mask & BRNF_DONT_TAKE_PARENT) ) {
+                        struct net_device *parent = bridge_parent(realindev);
+                        if (parent)
+                                realindev = parent;
+                }
 
                 NF_HOOK_THRESH(pf, NF_IP_FORWARD, skb, realindev,
                                realoutdev, br_nf_local_out_finish,
@@ -743,6 +763,9 @@ static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff **pskb,
         if (!nf_bridge)
                 return NF_ACCEPT;
 
+        if (!realoutdev)
+                return NF_DROP;
+
         if (skb->protocol == __constant_htons(ETH_P_IP) || IS_VLAN_IP)
                 pf = PF_INET;
         else