linux-kernel - Re: [PATCH] crypto: hisilicon/hpre - Fix a erroneous check after snprintf()

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Message-ID: <5c345399-46d7-f2e6-3700-427ab864e091@huawei.com>
Date:   Mon, 11 Sep 2023 09:52:28 +0800
From:   liulongfang <liulongfang@...wei.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Herbert Xu <herbert@...dor.apana.org.au>
CC:     "David S. Miller" <davem@...emloft.net>,
        Zaibo Xu <xuzaibo@...wei.com>, <linux-kernel@...r.kernel.org>,
        <kernel-janitors@...r.kernel.org>, <linux-crypto@...r.kernel.org>
Subject: Re: [PATCH] crypto: hisilicon/hpre - Fix a erroneous check after
 snprintf()

On 2023/9/9 0:11, Christophe JAILLET wrote:
> Le 06/09/2023 à 04:04, liulongfang a écrit :
>> On 2023/9/5 16:17, Herbert Xu wrote:
>>> On Tue, Sep 05, 2023 at 07:27:47AM +0200, Marion & Christophe JAILLET wrote:
>>>>
>>>> Some debugfs dir of file way be left around. Is it what your are talking
>>>> about?
>>>
>>> Yes all allocated resources should be freed on the error path.
>>>
>>>>> The other snprintf in the same file also looks suspect.
>>>>
>>>> It looks correct to me.
>>>>
>>>> And HPRE_DBGFS_VAL_MAX_LEN being 20, it doesn't really matter. The string
>>>> can't be truncated with just a "%u\n".
>>>
>>> Well if you're going to go with that line of reasoning then this
>>> case ("cluster%d") can't overflow either, no?
>>>
>>
>> First, I checked the calling code of the snprintf function in all driver files in
>> the hisilicon directory. Only here is the processing of return value judgment.
>> This treatment is indeed problematic and needs to be modified.
>>
>> Then, I don't quite agree with your modification plan.
>> The modification of this solution is not complete.
>> As Herbert said, ("cluster%d") may still have overflow problems.
> 
> Herbert said the contrary, and I agree with him.
> 
> HPRE_DBGFS_VAL_MAX_LEN is 20.
> 
> cluster%u will be at max:
>     strlen("cluster") + strlen("4294967295") + 1 = 17
> 
> (unless some system have 64 bits int?)
> 
> I do agree that it is safe to remove the test after snprintf(), but there is no need from my POV to turn "i" into a u8.
>

OK, your analysis makes sense.

Thanks.
Longfang.

> CJ
> 
>>
>> In the end, my proposed modification scheme is this:
>> ...
>>     int ret;
>>     u8 i;
>>
>>     for (i = 0; i < clusters_num; i++) {
>>         snprintf(buf, HPRE_DBGFS_VAL_MAX_LEN, "cluster%u", i);
>>         tmp_d = debugfs_create_dir(buf, qm->debug.debug_root);
>>         ...
>>     }
>> ...
>>
>> Thanks,
>> Longfang.
>>
>>> Cheers,
>>>
>>
> 
> .
>