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ipv6: fix possible UAF in ip6_finish_output2()

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[ Upstream commit da273b377a ]

If skb_expand_head() returns NULL, skb has been freed
and associated dst/idev could also have been freed.

We need to hold rcu_read_lock() to make sure the dst and
associated idev are alive.

Fixes: 5796015fa9 ("ipv6: allocate enough headroom in ip6_finish_output2()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Vasily Averin <vasily.averin@linux.dev>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20240820160859.3786976-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Eric Dumazet
2024-08-20 16:08:58 +00:00
committed by Greg Kroah-Hartman
parent 24e93695b1
commit e891b36de1
1 changed files with 4 additions and 0 deletions
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net/ipv6/ip6_output.c
+4
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@@ -69,11 +69,15 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
/* Be paranoid, rather than too clever. */
if (unlikely(hh_len > skb_headroom(skb)) && dev->header_ops) {
/* Make sure idev stays alive */
rcu_read_lock();
skb = skb_expand_head(skb, hh_len);
if (!skb) {
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
rcu_read_unlock();
return -ENOMEM;
}
rcu_read_unlock();
}
hdr = ipv6_hdr(skb);