linux-kernel - Re: [PATCH] btrfs: replace snprintf in show functions with sysfs

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Date:   Wed, 13 Oct 2021 18:49:12 +0800
From:   Qu Wenruo <quwenruo.btrfs@....com>
To:     dsterba@...e.cz, Anand Jain <anand.jain@...cle.com>,
        Qing Wang <wangqing@...o.com>, Chris Mason <clm@...com>,
        Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] btrfs: replace snprintf in show functions with sysfs_emit



On 2021/10/13 18:36, David Sterba wrote:
> On Wed, Oct 13, 2021 at 03:51:33PM +0800, Anand Jain wrote:
>> On 13/10/2021 11:28, Qing Wang wrote:
>>> coccicheck complains about the use of snprintf() in sysfs show functions.
>>
>> It looks like the reason is snprintf() unaware of the PAGE_SIZE
>> max_limit of the buf.
>>
>>> Fix the following coccicheck warning:
>>> fs/btrfs/sysfs.c:335:8-16: WARNING: use scnprintf or sprintf.

IIRC sprintf() is less safe than snprintf().
Is the check really correct to mention sprintf()?

>>
>> Hm. We use snprintf() at quite a lot more places in sysfs.c and, I don't
>> see them getting this fix. Why?
>
> I guess the patch is only addressing the warning for snprintf, reading
> the sources would show how many more conversions could have been done of
> scnprintf calls.
>
>>> Use sysfs_emit instead of scnprintf or sprintf makes more sense.
>>
>> Below commit has added it. Nice.
>>
>> commit 2efc459d06f1630001e3984854848a5647086232
>> Date:   Wed Sep 16 13:40:38 2020 -0700
>>
>>       sysfs: Add sysfs_emit and sysfs_emit_at to format sysfs out
>
> The conversion to the standard helper is good, but should be done
> in the entire file.
>

Yeah, the same idea, all sysfs interface should convert to the new
interface, not only the snprintf().

Thanks,
Qu