linux-kernel - Re: [PATCH] thinkpad_acpi: fix: use scnprintf instead of snprintf.

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Date:   Fri, 15 Jan 2021 16:27:18 -0300
From:   Henrique de Moraes Holschuh <hmh@....eng.br>
To:     Joe Perches <joe@...ches.com>
Cc:     YANG LI <abaci-bugfix@...ux.alibaba.com>, hdegoede@...hat.com,
        mgross@...ux.intel.com, ibm-acpi@....eng.br,
        ibm-acpi-devel@...ts.sourceforge.net,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thinkpad_acpi: fix: use scnprintf instead of snprintf.

On Wed, 06 Jan 2021, Joe Perches wrote:
> On Wed, 2021-01-06 at 14:36 +0800, YANG LI wrote:
> > The snprintf() function returns the number of characters which would
> > have been printed if there were enough space, but the scnprintf()
> > returns the number of characters which were actually printed. If the
> > buffer is not large enough, then using snprintf() would result in a
> > read overflow and an information leak. This error was found with the
> > help of coccicheck.
> 
> In all cases, the buffer _is_ large enough.

Thank you for double-checking!

> _show function lengths are OK for all the uses with PAGE_SIZE.
> And it's probably better to use sysfs_emit for all the _show functions

Indeed.

-- 
  Henrique Holschuh