linux-hardening - Re: [PATCH] mod_devicetable: Enlarge the maximum platform_device

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Message-ID: <Z_9SIBPsf4_cQ77Y@smile.fi.intel.com>
Date: Wed, 16 Apr 2025 09:45:52 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Kees Cook <kees@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nipun Gupta <nipun.gupta@....com>,
	Nikhil Agarwal <nikhil.agarwal@....com>,
	"Borislav Petkov (AMD)" <bp@...en8.de>,
	Pieter Jansen van Vuuren <pieter.jansen-van-vuuren@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>, Mark Brown <broonie@...nel.org>,
	Wesley Cheng <quic_wcheng@...cinc.com>,
	Tony Luck <tony.luck@...el.com>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] mod_devicetable: Enlarge the maximum platform_device_id
 name length

On Tue, Apr 15, 2025 at 04:14:24PM -0700, Kees Cook wrote:
> The 20 byte length of struct platform_device_id::name is not long enough
> for many devices (especially regulators), where the string initialization
> is getting truncated and missing the trailing NUL byte. This is seen
> with GCC 15's -Wunterminated-string-initialization option:
> 
> drivers/regulator/hi6421v530-regulator.c:189:19: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   189 |         { .name = "hi6421v530-regulator" },
>       |                   ^~~~~~~~~~~~~~~~~~~~~~
> drivers/regulator/hi6421v600-regulator.c:278:19: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   278 |         { .name = "hi6421v600-regulator" },
>       |                   ^~~~~~~~~~~~~~~~~~~~~~
> drivers/regulator/lp87565-regulator.c:233:11: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   233 |         { "lp87565-q1-regulator", },
>       |           ^~~~~~~~~~~~~~~~~~~~~~
> sound/soc/fsl/imx-pcm-rpmsg.c:818:19: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   818 |         { .name = "rpmsg-micfil-channel" },
>       |                   ^~~~~~~~~~~~~~~~~~~~~~
> drivers/iio/light/hid-sensor-als.c:457:25: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   457 |                 .name = "HID-SENSOR-LISS-0041",
>       |                         ^~~~~~~~~~~~~~~~~~~~~~
> drivers/iio/light/hid-sensor-prox.c:366:25: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (21 chars into 20 available) [-Wunterminated-string-initialization]
>   366 |                 .name = "HID-SENSOR-LISS-0226",
>       |                         ^~~~~~~~~~~~~~~~~~~~~~
> 
> Increase the length to 24, slightly more than is currently being used by
> the affected drivers. The string is used in '%s' format strings and via
> the module code, which appears to do its own length encoding. This size
> was chosen because there was already a 4 byte hole in the structure:
> 
> struct platform_device_id {
>         char                       name[20];             /*     0    20 */
> 
>         /* XXX 4 bytes hole, try to pack */
> 
>         kernel_ulong_t             driver_data;          /*    24     8 */
> 
>         /* size: 32, cachelines: 1, members: 2 */
>         /* sum members: 28, holes: 1, sum holes: 4 */
>         /* last cacheline: 32 bytes */
> };

Since there is no even potential ABI breakage, I'm fine with the change.
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

-- 
With Best Regards,
Andy Shevchenko