netdev - [PATCH 7/9] netfilter: ctnetlink: avoid null pointer dereference

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Date:   Wed, 13 Jun 2018 12:56:58 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 7/9] netfilter: ctnetlink: avoid null pointer dereference

From: Florian Westphal <fw@...len.de>

Dan Carpenter points out that deref occurs after NULL check, we should
re-fetch the pointer and check that instead.

Fixes: 2c205dd3981f7 ("netfilter: add struct nf_nat_hook and use it")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_conntrack_netlink.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 39327a42879f..20a2e37c76d1 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -1446,7 +1446,8 @@ ctnetlink_parse_nat_setup(struct nf_conn *ct,
 		}
 		nfnl_lock(NFNL_SUBSYS_CTNETLINK);
 		rcu_read_lock();
-		if (nat_hook->parse_nat_setup)
+		nat_hook = rcu_dereference(nf_nat_hook);
+		if (nat_hook)
 			return -EAGAIN;
 #endif
 		return -EOPNOTSUPP;
-- 
2.11.0