ipv4: early demux should be aware of fragments

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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 1 deletions

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;