linux-kernel - Re: [PATCH 3/5] video: fbdev: uvesafb.c: Cleaning up missing null-terminate by switching from strncpy to strzcpy

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Message-ID: <CAMuHMdV-2-t_NaH04pS4nRskDXswn7j2nuxSxp0gOAHfvTJ7FQ@mail.gmail.com>
Date:	Mon, 20 Oct 2014 09:10:37 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
Cc:	Michal Januszewski <spock@...too.org>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Andi Kleen <ak@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Grant Likely <grant.likely@...aro.org>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] video: fbdev: uvesafb.c: Cleaning up missing
 null-terminate by switching from strncpy to strzcpy

On Sun, Oct 19, 2014 at 12:14 AM, Rickard Strandqvist
<rickard_strandqvist@...ctrumdigital.se> wrote:
> Ensures that the string is null-terminate in connection with the
> use of strncpy, by switching from strncpy to strzcpy.
>
> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
> ---
>  drivers/video/fbdev/uvesafb.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/video/fbdev/uvesafb.c b/drivers/video/fbdev/uvesafb.c
> index 509d452..3383b34 100644
> --- a/drivers/video/fbdev/uvesafb.c
> +++ b/drivers/video/fbdev/uvesafb.c
> @@ -1892,7 +1892,7 @@ static ssize_t show_v86d(struct device_driver *dev, char *buf)
>  static ssize_t store_v86d(struct device_driver *dev, const char *buf,
>                 size_t count)
>  {
> -       strncpy(v86d_path, buf, PATH_MAX);
> +       strzcpy(v86d_path, buf, sizeof(v86d_path));

I think strlcpy() should be good enough here?
Or am I missing a reason why the rest of the buffer should be zero-filled?

Nevertheless, I think this (or an alternative) change should be applied to
stable, as call_usermodehelper() might crash by writing to sysfs.

>         return count;
>  }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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