linux-kernel - Re: [PATCH net] netlink: Fix off-by-one error in netlink_proto

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Message-ID: <a88119f3-3968-e072-6caa-8229e2e470bf@huawei.com>
Date: Tue, 29 Oct 2024 09:30:58 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
CC: <a.kovaleva@...ro.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<horms@...nel.org>, <kuba@...nel.org>, <linux-kernel@...r.kernel.org>,
	<lirongqing@...du.com>, <netdev@...r.kernel.org>, <pabeni@...hat.com>
Subject: Re: [PATCH net] netlink: Fix off-by-one error in netlink_proto_init()



On 2024/10/29 2:24, Kuniyuki Iwashima wrote:
> From: Jinjie Ruan <ruanjinjie@...wei.com>
> Date: Mon, 28 Oct 2024 16:05:15 +0800
>> In the error path of netlink_proto_init(), frees the already allocated
>> bucket table for new hash tables in a loop, but the loop condition
>> terminates when the index reaches zero, which fails to free the first
>> bucket table at index zero.
>>
>> Check for >= 0 so that nl_table[0].hash is freed as well.
>>
>> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
>> ---
>>  net/netlink/af_netlink.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
>> index 0a9287fadb47..9601b85dda95 100644
>> --- a/net/netlink/af_netlink.c
>> +++ b/net/netlink/af_netlink.c
>> @@ -2936,7 +2936,7 @@ static int __init netlink_proto_init(void)
>>  	for (i = 0; i < MAX_LINKS; i++) {
>>  		if (rhashtable_init(&nl_table[i].hash,
>>  				    &netlink_rhashtable_params) < 0) {
>> -			while (--i > 0)
>> +			while (--i >= 0)
>>  				rhashtable_destroy(&nl_table[i].hash);
>>  			kfree(nl_table);
>>  			goto panic;
> 
> I remember the same question was posted in the past.
> https://lore.kernel.org/netdev/ZfOalln%2FmyRNOkH6@cy-server/
> 
> As Eric alreday pointed out (and as mentioned in the thread above too),
> it's going to panic, and we need not clean up resources here, so let's
> remove rhashtable_destroy() and kfree() instead of adjusting the loop
> condition.

Thank you very much, remove it is fine.

>