Hi Kees,

I love your patch! Yet something to improve:

[auto build test ERROR on staging/staging-testing]
[also build test ERROR on linus/master v5.14-rc3]
[cannot apply to wireless-drivers-next/master wireless-drivers/master next-20210727]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Kees-Cook/Introduce-strict-memcpy-bounds-checking/20210728-053749
base:   https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git 39f9137268ee3df0047706df4e9b7357a40ffc98
config: powerpc64-buildonly-randconfig-r002-20210726 (attached as .config)
compiler: powerpc-linux-gcc (GCC) 10.3.0
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://github.com/0day-ci/linux/commit/d6aff26cc627e1579f89ebaaa51365cabd5c7ee3
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Kees-Cook/Introduce-strict-memcpy-bounds-checking/20210728-053749
        git checkout d6aff26cc627e1579f89ebaaa51365cabd5c7ee3
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.3.0 make.cross ARCH=powerpc64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All errors (new ones prefixed by >>):

   In file included from include/linux/string.h:253,
                    from include/linux/bitmap.h:10,
                    from include/linux/cpumask.h:12,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/rcupdate.h:29,
                    from include/linux/rculist.h:11,
                    from include/linux/pid.h:5,
                    from include/linux/sched.h:14,
                    from arch/powerpc/kernel/signal_32.c:16:
   In function 'fortify_memset_chk',
       inlined from 'restore_user_regs.part.0' at arch/powerpc/kernel/signal_32.c:539:3:
>> include/linux/fortify-string.h:195:4: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
     195 |    __write_overflow_field();
         |    ^~~~~~~~~~~~~~~~~~~~~~~~
   cc1: all warnings being treated as errors


vim +/__write_overflow_field +195 include/linux/fortify-string.h

   177	
   178	__FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size,
   179						 const size_t p_size,
   180						 const size_t p_size_field)
   181	{
   182		if (__builtin_constant_p(size)) {
   183			/*
   184			 * Length argument is a constant expression, so we
   185			 * can perform compile-time bounds checking where
   186			 * buffer sizes are known.
   187			 */
   188	
   189			/* Error when size is larger than enclosing struct. */
   190			if (p_size > p_size_field && p_size < size)
   191				__write_overflow();
   192	
   193			/* Warn when write size is larger than dest field. */
   194			if (p_size_field < size)
 > 195				__write_overflow_field();
   196		}
   197		/*
   198		 * At this point, length argument may not be a constant expression,
   199		 * so run-time bounds checking can be done where buffer sizes are
   200		 * known. (This is not an "else" because the above checks may only
   201		 * be compile-time warnings, and we want to still warn for run-time
   202		 * overflows.)
   203		 */
   204	
   205		/*
   206		 * Always stop accesses beyond the struct that contains the
   207		 * field, when the buffer's remaining size is known.
   208		 * (The -1 test is to optimize away checks where the buffer
   209		 * lengths are unknown.)
   210		 */
   211		if (p_size != (size_t)(-1) && p_size < size)
   212			fortify_panic("memset");
   213	}
   214	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org