linux-kernel - [PATCH net v2] netfilter: nf_nat: Fix possible memory leak in nf_nat

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Date:   Tue, 1 Nov 2022 19:52:52 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
        <coreteam@...filter.org>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>
CC:     <pablo@...filter.org>, <kadlec@...filter.org>, <fw@...len.de>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <ast@...nel.org>, <lorenzo@...nel.org>,
        <john.fastabend@...il.com>, <chenzhongjin@...wei.com>
Subject: [PATCH net v2] netfilter: nf_nat: Fix possible memory leak in nf_nat_init()

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>
---
Also revert the operation for &follow_master_nat and nf_nat_hook,
then slightly fix commit msg for it.
---
 net/netfilter/nf_nat_core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nf_nat_core.c b/net/netfilter/nf_nat_core.c
index 18319a6e6806..47aa67abd531 100644
--- a/net/netfilter/nf_nat_core.c
+++ b/net/netfilter/nf_nat_core.c
@@ -1152,7 +1152,15 @@ 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)
-- 
2.17.1