From bba90d3686fd0e2de7b058fbbf2d314527a20d49 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 14 Sep 2018 12:02:31 -0700 Subject: [PATCH] ipv6: fix possible use-after-free in ip6_xmit() [ Upstream commit bbd6528d28c1b8e80832b3b018ec402b6f5c3215 ] In the unlikely case ip6_xmit() has to call skb_realloc_headroom(), we need to call skb_set_owner_w() before consuming original skb, otherwise we risk a use-after-free. Bring IPv6 in line with what we do in IPv4 to fix this. Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet Reported-by: syzbot Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index 1da021527fcd..9ab1e0fcbc13 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -219,12 +219,10 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, kfree_skb(skb); return -ENOBUFS; } + if (skb->sk) + skb_set_owner_w(skb2, skb->sk); consume_skb(skb); skb = skb2; - /* skb_set_owner_w() changes sk->sk_wmem_alloc atomically, - * it is safe to call in our context (socket lock not held) - */ - skb_set_owner_w(skb, (struct sock *)sk); } if (opt->opt_flen) ipv6_push_frag_opts(skb, opt, &proto);