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Subject[PATCH 5.4 047/109] netfilter: conntrack: refetch conntrack after nf_conntrack_update()
Date
From: Pablo Neira Ayuso <pablo@netfilter.org>

[ Upstream commit d005fbb855d3b5660d62ee5a6bd2d99c13ff8cf3 ]

__nf_conntrack_update() might refresh the conntrack object that is
attached to the skbuff. Otherwise, this triggers UAF.

[ 633.200434] ==================================================================
[ 633.200472] BUG: KASAN: use-after-free in nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200478] Read of size 1 at addr ffff888370804c00 by task nfqnl_test/6769

[ 633.200487] CPU: 1 PID: 6769 Comm: nfqnl_test Not tainted 5.8.0-rc2+ #388
[ 633.200490] Hardware name: LENOVO 23259H1/23259H1, BIOS G2ET32WW (1.12 ) 05/30/2012
[ 633.200491] Call Trace:
[ 633.200499] dump_stack+0x7c/0xb0
[ 633.200526] ? nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200532] print_address_description.constprop.6+0x1a/0x200
[ 633.200539] ? _raw_write_lock_irqsave+0xc0/0xc0
[ 633.200568] ? nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200594] ? nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200598] kasan_report.cold.9+0x1f/0x42
[ 633.200604] ? call_rcu+0x2c0/0x390
[ 633.200633] ? nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200659] nf_conntrack_update+0x34e/0x770 [nf_conntrack]
[ 633.200687] ? nf_conntrack_find_get+0x30/0x30 [nf_conntrack]

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1436
Fixes: ee04805ff54a ("netfilter: conntrack: make conntrack userspace helpers work again")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_conntrack_core.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 48db4aec02dea..200cdad3ff3ab 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -2012,6 +2012,8 @@ static int nf_conntrack_update(struct net *net, struct sk_buff *skb)
err = __nf_conntrack_update(net, skb, ct, ctinfo);
if (err < 0)
return err;
+
+ ct = nf_ct_get(skb, &ctinfo);
}

return nf_confirm_cthelper(skb, ct, ctinfo);
--
2.25.1


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