Re: [PATCH] btrfs: replace snprintf in show functions with sysfs_emit

[Qu Wenruo]

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