ipv6: fix NULL reference in proxy neighbor discovery

The addition of TLLAO option created a kernel OOPS regression
for the case where neighbor advertisement is being sent via
proxy path.  When using proxy, ipv6_get_ifaddr() returns NULL
causing the NULL dereference.

Change causing the bug was:
commit f7734fdf61ec6bb848e0bafc1fb8bad2c124bb50
Author: Octavian Purdila <opurdila@ixiacom.com>
Date:   Fri Oct 2 11:39:15 2009 +0000

    make TLLAO option for NA packets configurable

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 0abdc242ddb76029cc2f6a52bed1bbdea2189364..2efef52fb4616fb5d598026a35ecf1d76aba0fd8 100644 (file)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -586,6 +586,7 @@ static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
                src_addr = solicited_addr;
                if (ifp->flags & IFA_F_OPTIMISTIC)
                        override = 0;
+               inc_opt |= ifp->idev->cnf.force_tllao;
                in6_ifa_put(ifp);
        } else {
                if (ipv6_dev_get_saddr(dev_net(dev), dev, daddr,
@@ -599,7 +600,6 @@ static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
        icmp6h.icmp6_solicited = solicited;
        icmp6h.icmp6_override = override;
 
-       inc_opt |= ifp->idev->cnf.force_tllao;
        __ndisc_send(dev, neigh, daddr, src_addr,
                     &icmp6h, solicited_addr,
                     inc_opt ? ND_OPT_TARGET_LL_ADDR : 0);