[PATCH 2/2] netfilter: ipvs/SIP: handle ip_vs_fill_iph_skb_off failure

To: Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, Julian Anastasov <ja@xxxxxx>
Subject: [PATCH 2/2] netfilter: ipvs/SIP: handle ip_vs_fill_iph_skb_off failure
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Arnd Bergmann <arnd@xxxxxxxx>, Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>, Patrick McHardy <kaber@xxxxxxxxx>, Jozsef Kadlecsik <kadlec@xxxxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, lvs-devel@xxxxxxxxxxxxxxx, netfilter-devel@xxxxxxxxxxxxxxx, coreteam@xxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
From: Arnd Bergmann <arnd@xxxxxxxx>
Date: Wed, 27 Jan 2016 14:52:02 +0100
ip_vs_fill_iph_skb_off() may not find an IP header, and gcc has
determined that ip_vs_sip_fill_param() then incorrectly accesses
the protocol fields:

net/netfilter/ipvs/ip_vs_pe_sip.c: In function 'ip_vs_sip_fill_param':
net/netfilter/ipvs/ip_vs_pe_sip.c:76:5: error: 'iph.protocol' may be used 
uninitialized in this function [-Werror=maybe-uninitialized]
  if (iph.protocol != IPPROTO_UDP)
net/netfilter/ipvs/ip_vs_pe_sip.c:81:10: error: 'iph.len' may be used 
uninitialized in this function [-Werror=maybe-uninitialized]
  dataoff = iph.len + sizeof(struct udphdr);

This adds a check for the ip_vs_fill_iph_skb_off() return code
before looking at the ip header data returned from it.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Fixes: b0e010c527de ("ipvs: replace ip_vs_fill_ip4hdr with 
 net/netfilter/ipvs/ip_vs_pe_sip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipvs/ip_vs_pe_sip.c 
index 1b8d594e493a..c4e9ca016a88 100644
--- a/net/netfilter/ipvs/ip_vs_pe_sip.c
+++ b/net/netfilter/ipvs/ip_vs_pe_sip.c
@@ -70,10 +70,10 @@ ip_vs_sip_fill_param(struct ip_vs_conn_param *p, struct 
sk_buff *skb)
        const char *dptr;
        int retc;
-       ip_vs_fill_iph_skb(p->af, skb, false, &iph);
+       retc = ip_vs_fill_iph_skb(p->af, skb, false, &iph);
        /* Only useful with UDP */
-       if (iph.protocol != IPPROTO_UDP)
+       if (!retc || iph.protocol != IPPROTO_UDP)
                return -EINVAL;
        /* todo: IPv6 fragments:
         *       I think this only should be done for the first fragment. /HS

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