Re: [PATCH] x86: Alias memset to __builtin_memset.

[Kees Cook <keescook@chromium.org>]

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On Tue, Mar 24, 2020 at 04:16:10AM +0800, kbuild test robot wrote:
> Hi Clement,
> 
> Thank you for the patch! Yet something to improve:
> 
> [auto build test ERROR on tip/x86/core]
> [also build test ERROR on v5.6-rc7 next-20200323]
> [if your patch is applied to the wrong git tree, please drop us a note to help
> improve the system. BTW, we also suggest to use '--base' option to specify the
> base tree in git format-patch, please see https://stackoverflow.com/a/37406982]
> 
> url:    https://github.com/0day-ci/linux/commits/Clement-Courbet/x86-Alias-memset-to-__builtin_memset/20200324-004007
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 248ed51048c40d36728e70914e38bffd7821da57
> config: x86_64-randconfig-h003-20200323 (attached as .config)
> compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 006244152d6c7dd6a390ff89b236cc7801834b46)
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         COMPILER=clang make.cross ARCH=x86_64 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
> 
> All errors (new ones prefixed by >>):
> 
>    In file included from scripts/mod/devicetable-offsets.c:3:
>    In file included from include/linux/mod_devicetable.h:13:
>    In file included from include/linux/uuid.h:12:
> >> include/linux/string.h:358:24: error: definition of builtin function '__builtin_memset'
>    __FORTIFY_INLINE void *memset(void *p, int c, __kernel_size_t size)
>                           ^
>    arch/x86/include/asm/string_64.h:27:29: note: expanded from macro 'memset'
>    #define memset(s, c, count) __builtin_memset(s, c, count)
>                                ^

This needs to be within #ifndef CONFIG_FORTIFY_SOURCE. FORTIFY already
does this. Additionally, shouldn't this just be done universally,
instead of in x86-specific code?

-Kees

>    1 error generated.
>    make[2]: *** [scripts/Makefile.build:99: scripts/mod/devicetable-offsets.s] Error 1
>    make[2]: Target '__build' not remade because of errors.
>    make[1]: *** [Makefile:1112: prepare0] Error 2
>    make[1]: Target 'prepare' not remade because of errors.
>    make: *** [Makefile:179: sub-make] Error 2
>    27 real  8 user  13 sys  79.89% cpu 	make prepare
> 
> vim +/__builtin_memset +358 include/linux/string.h
> 
> 6974f0c4555e28 Daniel Micay 2017-07-12  357  
> 6974f0c4555e28 Daniel Micay 2017-07-12 @358  __FORTIFY_INLINE void *memset(void *p, int c, __kernel_size_t size)
> 6974f0c4555e28 Daniel Micay 2017-07-12  359  {
> 6974f0c4555e28 Daniel Micay 2017-07-12  360  	size_t p_size = __builtin_object_size(p, 0);
> 6974f0c4555e28 Daniel Micay 2017-07-12  361  	if (__builtin_constant_p(size) && p_size < size)
> 6974f0c4555e28 Daniel Micay 2017-07-12  362  		__write_overflow();
> 6974f0c4555e28 Daniel Micay 2017-07-12  363  	if (p_size < size)
> 6974f0c4555e28 Daniel Micay 2017-07-12  364  		fortify_panic(__func__);
> 6974f0c4555e28 Daniel Micay 2017-07-12  365  	return __builtin_memset(p, c, size);
> 6974f0c4555e28 Daniel Micay 2017-07-12  366  }
> 6974f0c4555e28 Daniel Micay 2017-07-12  367  
> 
> :::::: The code at line 358 was first introduced by commit
> :::::: 6974f0c4555e285ab217cee58b6e874f776ff409 include/linux/string.h: add the option of fortified string.h functions
> 
> :::::: TO: Daniel Micay <danielmicay@gmail.com>
> :::::: CC: Linus Torvalds <torvalds@linux-foundation.org>
> 
> ---
> 0-DAY CI Kernel Test Service, Intel Corporation
> https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org
> 
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-- 
Kees Cook