4.15-stable review patch.  If anyone has any objections, please let me know.


From: Florian Westphal <f...@strlen.de>

commit b078556aecd791b0e5cb3a59f4c3a14273b52121 upstream.

l4proto->manip_pkt() can cause reallocation of skb head so pointer
to the ipv6 header must be reloaded.

Reported-and-tested-by: <syzbot+10005f4292fc9cc89...@syzkaller.appspotmail.com>
Fixes: 58a317f1061c89 ("netfilter: ipv6: add IPv6 NAT support")
Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

 net/ipv6/netfilter/nf_nat_l3proto_ipv6.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_nat_l3proto_ipv6.c
@@ -99,6 +99,10 @@ static bool nf_nat_ipv6_manip_pkt(struct
            !l4proto->manip_pkt(skb, &nf_nat_l3proto_ipv6, iphdroff, hdroff,
                                target, maniptype))
                return false;
+       /* must reload, offset might have changed */
+       ipv6h = (void *)skb->data + iphdroff;
        if (maniptype == NF_NAT_MANIP_SRC)
                ipv6h->saddr = target->src.u3.in6;

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