linux-kernel - Re: [PATCH 3/3] [v2] staging: greybus: change strncpy() to strscpy

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Date: Tue, 9 Apr 2024 10:04:17 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Viresh Kumar <vireshk@...nel.org>, Johan Hovold <johan@...nel.org>,
	Alex Elder <elder@...nel.org>,
	Justin Stitt <justinstitt@...gle.com>,
	Arnd Bergmann <arnd@...db.de>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	greybus-dev@...ts.linaro.org, linux-staging@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] [v2] staging: greybus: change strncpy() to
 strscpy_pad()

On Mon, Apr 08, 2024 at 09:48:11PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> gcc-10 warns about a strncpy() that does not enforce zero-termination:
> 
> In file included from include/linux/string.h:369,
>                  from drivers/staging/greybus/fw-management.c:9:
> In function 'strncpy',
>     inlined from 'fw_mgmt_backend_fw_update_operation' at drivers/staging/greybus/fw-management.c:306:2:
> include/linux/fortify-string.h:108:30: error: '__builtin_strncpy' specified bound 10 equals destination size [-Werror=stringop-truncation]
>   108 | #define __underlying_strncpy __builtin_strncpy
>       |                              ^
> include/linux/fortify-string.h:187:9: note: in expansion of macro '__underlying_strncpy'
>   187 |  return __underlying_strncpy(p, q, size);
>       |         ^~~~~~~~~~~~~~~~~~~~
> 
> For some reason, I cannot reproduce this with gcc-9 or gcc-11, and I only
> get a warning for one of the four related strncpy()s, so I'm not
> sure what's going on.
> 
> Change all four to strscpy_pad(), which is the safest replacement here,
> as it avoids ending up with uninitialized stack data in the tag name.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2
>  - use strscpy_pad()
>  - use two-argument form
>  - change all four instances, not just the one that produced the warning

Reviewed-by: Dan Carpenter <dan.carpenter@...aro.org>

regards,
dan carpenter