linux-kernel - Re: [RFC 0/7] eliminate snprintf with overlapping src and dst

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Message-ID: <CAGXu5jKSiCpg8kpOGzgwuhG7H-DEtOBuF4r_6e2cEfY2FA4zyQ@mail.gmail.com>
Date:	Tue, 8 Mar 2016 15:13:16 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 0/7] eliminate snprintf with overlapping src and dst

On Tue, Mar 8, 2016 at 12:40 PM, Rasmus Villemoes
<linux@...musvillemoes.dk> wrote:
> Doing snprintf(buf, len, "%s...", buf, ...) for appending to a buffer
> currently works, but it is somewhat fragile, and any other overlap
> between source and destination buffers would be a definite bug. This
> is an attempt at eliminating the relatively few occurences of this
> pattern in the kernel.
>
> I could use another set of eyes on all of these. The drm/amdkfd patch
> is unfortunately rather large, but I couldn't find a better way to do
> this.

Best alternative would be to have the macros just use side-effects to
bump "ret" without passing it in, etc, but that's ugly/fragile, so I'd
agree: what you have is best.

Consider all the changes:

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

>
> Rasmus Villemoes (7):
>   drm/amdkfd: avoid fragile and inefficient snprintf use
>   Input: joystick - avoid fragile snprintf use
>   leds: avoid fragile sprintf use
>   drivers/media/pci/zoran: avoid fragile snprintf use
>   wlcore: avoid fragile snprintf use
>   [media] ati_remote: avoid fragile snprintf use
>   USB: usbatm: avoid fragile and inefficient snprintf use
>
>  drivers/gpu/drm/amd/amdkfd/kfd_topology.c | 168 +++++++++++++++---------------
>  drivers/input/joystick/analog.c           |   8 +-
>  drivers/leds/led-class-flash.c            |   3 +-
>  drivers/media/pci/zoran/videocodec.c      |   5 +-
>  drivers/media/rc/ati_remote.c             |  11 +-
>  drivers/net/wireless/ti/wlcore/boot.c     |  12 ++-
>  drivers/usb/atm/usbatm.c                  |  11 +-
>  7 files changed, 110 insertions(+), 108 deletions(-)
>
> --
> 2.1.4
>



-- 
Kees Cook
Chrome OS & Brillo Security