linux-kernel - Re: [PATCH net] net: sched: fix possible refcount leak in tc_chain_tmplt

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Message-ID: <7a5e7377-4931-36e3-4102-8fcb1f7a81e8@gmail.com>
Date:   Wed, 7 Jun 2023 10:20:28 +0800
From:   Hangyu Hua <hbh25y@...il.com>
To:     Larysa Zaremba <larysa.zaremba@...el.com>
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: sched: fix possible refcount leak in
 tc_chain_tmplt_add()

On 6/6/2023 16:53, Larysa Zaremba wrote:
> On Mon, Jun 05, 2023 at 03:01:58PM +0800, Hangyu Hua wrote:
>> try_module_get can be called in tcf_proto_lookup_ops. So if ops don't
>> implement the corresponding function we should call module_put to drop
>> the refcount.
>>
> 
> Code seems reasonable. But commit message is pretty hard to understand.
> Please, replace "corresponding" with "required".
> Also change the first sentence, do not use "can". From what I see, successful
> execution of tcf_proto_lookup_ops always means we now hold reference to module.
> 
> CC me in v2, I'll give you Reviewed-by.
> 

I apologize for my incorrect English expression. I will send a v2 later.

Thanks,
Hangyu

>> Fixes: 9f407f1768d3 ("net: sched: introduce chain templates")
>> Signed-off-by: Hangyu Hua <hbh25y@...il.com>
>> ---
>>   net/sched/cls_api.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
>> index 2621550bfddc..92bfb892e638 100644
>> --- a/net/sched/cls_api.c
>> +++ b/net/sched/cls_api.c
>> @@ -2952,6 +2952,7 @@ static int tc_chain_tmplt_add(struct tcf_chain *chain, struct net *net,
>>   		return PTR_ERR(ops);
>>   	if (!ops->tmplt_create || !ops->tmplt_destroy || !ops->tmplt_dump) {
>>   		NL_SET_ERR_MSG(extack, "Chain templates are not supported with specified classifier");
>> +		module_put(ops->owner);
>>   		return -EOPNOTSUPP;
>>   	}
>>   
>> -- 
>> 2.34.1
>>
>>