linux-kernel - Re: [PATCH 17/22] platform/x86: alienware-wmi: fix format string overflow warning

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Message-ID: <CAHp75Vd2eZAj++QdGraspjpTX=VPVR6qY+iCZiHsySGvUcGVmQ@mail.gmail.com>
Date:   Fri, 14 Jul 2017 22:18:25 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        netdev <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        linux-scsi <linux-scsi@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH 17/22] platform/x86: alienware-wmi: fix format string
 overflow warning

On Fri, Jul 14, 2017 at 3:07 PM, Arnd Bergmann <arnd@...db.de> wrote:
> gcc points out a possible format string overflow for a large value of 'zone':
>
> drivers/platform/x86/alienware-wmi.c: In function 'alienware_wmi_init':
> drivers/platform/x86/alienware-wmi.c:461:24: error: '%02X' directive writing between 2 and 8 bytes into a region of size 6 [-Werror=format-overflow=]
>    sprintf(buffer, "zone%02X", i);
>                         ^~~~
> drivers/platform/x86/alienware-wmi.c:461:19: note: directive argument in the range [0, 2147483646]
>    sprintf(buffer, "zone%02X", i);
>                    ^~~~~~~~~~
> drivers/platform/x86/alienware-wmi.c:461:3: note: 'sprintf' output between 7 and 13 bytes into a destination of size 10
>
> While the zone should never be that large, it's easy to make the
> buffer a few bytes longer so gcc can prove this to be safe.

Please, be a bit smarter on such fixes.

Here we need to convert

int i;

to

u8 i;

I will take it after addressing above.

P.S. You may do this change across the file.

> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/platform/x86/alienware-wmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/alienware-wmi.c b/drivers/platform/x86/alienware-wmi.c
> index 0831b428c217..acc01242da82 100644
> --- a/drivers/platform/x86/alienware-wmi.c
> +++ b/drivers/platform/x86/alienware-wmi.c
> @@ -421,7 +421,7 @@ static DEVICE_ATTR(lighting_control_state, 0644, show_control_state,
>  static int alienware_zone_init(struct platform_device *dev)
>  {
>         int i;
> -       char buffer[10];
> +       char buffer[13];
>         char *name;
>
>         if (interface == WMAX) {
> --
> 2.9.0
>



-- 
With Best Regards,
Andy Shevchenko