Re: include/linux/fortify-string.h:52:29: warning: '__builtin_strcpy' source argument is the same as destination

Kees Cook
2023-11-30T22:11:59Z

On Thu, Nov 30, 2023 at 12:02:50PM +0800, kernel test robot wrote:
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: 3b47bc037bd44f142ac09848e8d3ecccc726be99
> commit: ba38961a069b0d8d03b53218a6c29d737577d448 um: Enable FORTIFY_SOURCE
> date: 1 year, 3 months ago
> config: um-randconfig-r034-20230830 (https://download.01.org/0day-ci/archive/20231130/202311301039.7i51bZCz-lkp@intel.com/config)
> compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231130/202311301039.7i51bZCz-lkp@intel.com/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202311301039.7i51bZCz-lkp@intel.com/
>
> [...]
> kernel/kallsyms.c: In function '__sprint_symbol.isra.0':
> >> include/linux/fortify-string.h:52:29: warning: '__builtin_strcpy' source argument is the same as destination [-Wrestrict]
> 52 | #define __underlying_strcpy __builtin_strcpy
> | ^
> include/linux/fortify-string.h:567:10: note: in expansion of macro '__underlying_strcpy'
> 567 | return __underlying_strcpy(p, q);
> | ^~~~~~~~~~~~~~~~~~~

The only strcpy() in __sprint_symbol() is:

if (name != buffer)
strcpy(buffer, name);

Which is explicitly not the same address...

This appears to be a GCC 9 false positive, maybe?

--
Kees Cook