netdev - Re: [PATCH net] net: netfilter: Fix use-after-free in get

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Message-ID: <e4336ee6-31c1-4299-bddc-4c3072e03065@huawei.com>
Date: Wed, 23 Oct 2024 15:03:35 +0800
From: "dongchenchen (A)" <dongchenchen2@...wei.com>
To: Florian Westphal <fw@...len.de>
CC: <pablo@...filter.org>, <kadlec@...filter.org>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<kuniyu@...zon.com>, <netfilter-devel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <yuehaibing@...wei.com>
Subject: Re: [PATCH net] net: netfilter: Fix use-after-free in get_info()


On 2024/10/22 17:48, Florian Westphal wrote:
> Dong Chenchen <dongchenchen2@...wei.com> wrote:
>>   net/netfilter/x_tables.c | 8 +++++---
>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
>> index da5d929c7c85..359c880ecb07 100644
>> --- a/net/netfilter/x_tables.c
>> +++ b/net/netfilter/x_tables.c
>> @@ -1239,6 +1239,7 @@ struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
>>   	struct module *owner = NULL;
>>   	struct xt_template *tmpl;
>>   	struct xt_table *t;
>> +	int err = -ENOENT;
>>   
>>   	mutex_lock(&xt[af].mutex);
>>   	list_for_each_entry(t, &xt_net->tables[af], list)
>> @@ -1247,8 +1248,6 @@ struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
>>   
>>   	/* Table doesn't exist in this netns, check larval list */
>>   	list_for_each_entry(tmpl, &xt_templates[af], list) {
>> -		int err;
>> -
>>   		if (strcmp(tmpl->name, name))
>>   			continue;
>>   		if (!try_module_get(tmpl->me))
>> @@ -1267,6 +1266,9 @@ struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
>>   		break;
>>   	}
>>   
>> +	if (err < 0)
>> +		goto out;
>> +
>>   	/* and once again: */
>>   	list_for_each_entry(t, &xt_net->tables[af], list)
>>   		if (strcmp(t->name, name) == 0)
> Proabably also:
>
> -  		if (strcmp(t->name, name) == 0)
> +               if (strcmp(t->name, name) == 0 && owner == t->me)

Hi, Florian. Thank you very much for your suggestions!

If err <0 , xt_table does not exist in the xt_net list or the tmpl list.

And  list operations are performed in the mutex lock.

Therefore, it may not be necessary to traverse the xt_net list again.