Re: include/linux/fortify-string.h:220:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()?

["Chen, Rong A" <rong.a.chen@intel.com>]

On 10/29/2022 6:03 AM, Kees Cook wrote:
> On Sun, Oct 23, 2022 at 04:45:58AM +0800, kernel test robot wrote:
>> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>> head:   4da34b7d175dc99b8befebd69e96546c960d526c
>> commit: 28e77cc1c0686621a4d416f599cee5ab369daa0a fortify: Detect struct member overflows in memset() at compile-time
>> date:   8 months ago
>> config: arm-randconfig-r012-20221023
>> compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
>> reproduce (this is a W=1 build):
>>          wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>>          chmod +x ~/bin/make.cross
>>          # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=28e77cc1c0686621a4d416f599cee5ab369daa0a
>>          git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>>          git fetch --no-tags linus master
>>          git checkout 28e77cc1c0686621a4d416f599cee5ab369daa0a
>>          # save the config file
>>          mkdir build_dir && cp config build_dir/.config
>>          COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash fs/ocfs2/
>>
>> If you fix the issue, kindly add following tag where applicable
>> | Reported-by: kernel test robot <lkp@intel.com>
>>
>> All warnings (new ones prefixed by >>):
>>
>>     In file included from include/linux/string.h:253,
>>                      from include/linux/bitmap.h:11,
>>                      from include/linux/cpumask.h:12,
>>                      from include/linux/smp.h:13,
>>                      from include/linux/lockdep.h:14,
>>                      from include/linux/spinlock.h:62,
>>                      from include/linux/mmzone.h:8,
>>                      from include/linux/gfp.h:6,
>>                      from include/linux/slab.h:15,
>>                      from fs/ocfs2/dlmglue.c:11:
>>     In function 'fortify_memset_chk',
>>         inlined from 'ocfs2_lock_res_free' at fs/ocfs2/dlmglue.c:790:2:
>>>> include/linux/fortify-string.h:220:25: warning: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribute-warning]
>>       220 |                         __write_overflow_field(p_size_field, size);
>>           |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This appears to be a compiler bug. The line in question is:
> 
>          memset(&res->l_lksb, 0, sizeof(res->l_lksb));
> 
> Looking at binary output, something is failing in dead code elimination,
> as the copy of the code holding this is never called, and has a
> non-literal value for the __builtin_object_size() output, which isn't
> possible.
> 
> -Kees
> 


Hi Kees,

Thanks for your feedback, we'll add it to ignore list.

Best Regards,
Rong Chen