netdev - [PATCH net 6/7] netfilter: nf_nat: Fix possible memory leak in nf_nat

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Date:   Wed,  2 Nov 2022 19:46:58 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com
Subject: [PATCH net 6/7] netfilter: nf_nat: Fix possible memory leak in nf_nat_init()

From: Chen Zhongjin <chenzhongjin@...wei.com>

In nf_nat_init(), register_nf_nat_bpf() can fail and return directly
without any error handling.
Then nf_nat_bysource will leak and registering of &nat_net_ops,
&follow_master_nat and nf_nat_hook won't be reverted.

This leaves wild ops in linkedlists and when another module tries to
call register_pernet_operations() or nf_ct_helper_expectfn_register()
it triggers page fault:

 BUG: unable to handle page fault for address: fffffbfff81b964c
 RIP: 0010:register_pernet_operations+0x1b9/0x5f0
 Call Trace:
 <TASK>
  register_pernet_subsys+0x29/0x40
  ebtables_init+0x58/0x1000 [ebtables]
  ...

Fixes: 820dc0523e05 ("net: netfilter: move bpf_ct_set_nat_info kfunc in nf_nat_bpf.c")
Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_nat_core.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 18319a6e6806..e29e4ccb5c5a 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -1152,7 +1152,16 @@ static int __init nf_nat_init(void)
 	WARN_ON(nf_nat_hook != NULL);
 	RCU_INIT_POINTER(nf_nat_hook, &nat_hook);
 
-	return register_nf_nat_bpf();
+	ret = register_nf_nat_bpf();
+	if (ret < 0) {
+		RCU_INIT_POINTER(nf_nat_hook, NULL);
+		nf_ct_helper_expectfn_unregister(&follow_master_nat);
+		synchronize_net();
+		unregister_pernet_subsys(&nat_net_ops);
+		kvfree(nf_nat_bysource);
+	}
+
+	return ret;
 }
 
 static void __exit nf_nat_cleanup(void)
-- 
2.30.2