netdev - [PATCH net] ipv4: early demux should be aware of fragments

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Date:	Tue, 26 Jan 2016 16:59:42 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Joe Stringer <joe@....org>, David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>, fw@...len.de,
	hannes@...essinduktion.org, pravin shelar <pshelar@....org>
Subject: [PATCH net] ipv4: early demux should be aware of fragments

From: Eric Dumazet <edumazet@...gle.com>

We should not assume a valid protocol header is present,
as this is not the case for IPv4 fragments.

Lets avoid extra cache line misses and potential bugs
if we actually find a socket and incorrectly uses its dst.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/ip_input.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index b1209b63381f..d77eb0c3b684 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -316,7 +316,10 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 	const struct iphdr *iph = ip_hdr(skb);
 	struct rtable *rt;
 
-	if (sysctl_ip_early_demux && !skb_dst(skb) && !skb->sk) {
+	if (sysctl_ip_early_demux &&
+	    !skb_dst(skb) &&
+	    !skb->sk &&
+	    !ip_is_fragment(iph)) {
 		const struct net_protocol *ipprot;
 		int protocol = iph->protocol;