netfilter: bridge: fix NULL deref in physin/out ifindex helpers

Might not have an outdev yet. We'll oops when iface goes down while skbs
are still nfqueue'd:

RIP: 0010:[<ffffffff81422a2f>]  [<ffffffff81422a2f>] dev_cmp+0x4f/0x80
nfqnl_rcv_dev_event+0xe2/0x150
notifier_call_chain+0x53/0xa0

Fixes: c737b7c4510026 ("netfilter: bridge: add helpers for fetching physin/outdev")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 14 insertions, 2 deletions

diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
index ab8f76dba668..f2fdb5a52070 100644
--- a/include/linux/netfilter_bridge.h
+++ b/include/linux/netfilter_bridge.h
@@ -39,12 +39,24 @@ static inline void br_drop_fake_rtable(struct sk_buff *skb)
 
 static inline int nf_bridge_get_physinif(const struct sk_buff *skb)
 {
-        return skb->nf_bridge ? skb->nf_bridge->physindev->ifindex : 0;
+        struct nf_bridge_info *nf_bridge;
+
+        if (skb->nf_bridge == NULL)
+                return 0;
+
+        nf_bridge = skb->nf_bridge;
+        return nf_bridge->physindev ? nf_bridge->physindev->ifindex : 0;
 }
 
 static inline int nf_bridge_get_physoutif(const struct sk_buff *skb)
 {
-        return skb->nf_bridge ? skb->nf_bridge->physoutdev->ifindex : 0;
+        struct nf_bridge_info *nf_bridge;
+
+        if (skb->nf_bridge == NULL)
+                return 0;
+
+        nf_bridge = skb->nf_bridge;
+        return nf_bridge->physoutdev ? nf_bridge->physoutdev->ifindex : 0;
 }
 
 static inline struct net_device *