netfilter: Fix potential use after free in ip6_route_me_harder()

commit a8951d5814e1373807a94f79f7ccec7041325470 upstream.

Dst is released one line before we access it again with dst->error.

Fixes: 58e35d147128 netfilter: ipv6: propagate routing errors from
ip6_route_me_harder()

Signed-off-by: Sergey Popovich <popovich_sergei@mail.ru>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index 95f3f1d..d38e6a8 100644 (file)
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -30,13 +30,15 @@ int ip6_route_me_harder(struct sk_buff *skb)
                .daddr = iph->daddr,
                .saddr = iph->saddr,
        };
+       int err;
 
        dst = ip6_route_output(net, skb->sk, &fl6);
-       if (dst->error) {
+       err = dst->error;
+       if (err) {
                IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
                LIMIT_NETDEBUG(KERN_DEBUG "ip6_route_me_harder: No more route.\n");
                dst_release(dst);
-               return dst->error;
+               return err;
        }
 
        /* Drop old route. */