From bbd6528d28c1b8e80832b3b018ec402b6f5c3215 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 14 Sep 2018 12:02:31 -0700
Subject: [PATCH] ipv6: fix possible use-after-free in ip6_xmit()
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 <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
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 16f200f065007..f9f8f554d1416 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);
--
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