include/linux/fortify-string.h:47:30: warning: '__builtin_strncat' output truncated before terminating nul copying as many bytes from a string as its length

[kernel test robot]

Hi Steven,

FYI, the error/warning still remains.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   143a6252e1b8ab424b4b293512a97cca7295c182
commit: 9f8e5aee93ed2482638d577a56806b455084b595 tracing: Fix allocation of last_cmd in last_cmd_set()
date:   3 months ago
config: x86_64-rhel-8.3 (https://download.01.org/0day-ci/archive/20220524/202205241717.IZu66s3A-lkp@xxxxxxxxx/config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9f8e5aee93ed2482638d577a56806b455084b595
        git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
        git fetch --no-tags linus master
        git checkout 9f8e5aee93ed2482638d577a56806b455084b595
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/trace/

If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <lkp@xxxxxxxxx>

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 arch/x86/include/asm/cpumask.h:5,
                    from arch/x86/include/asm/msr.h:11,
                    from arch/x86/include/asm/processor.h:22,
                    from arch/x86/include/asm/timex.h:5,
                    from include/linux/timex.h:65,
                    from include/linux/time32.h:13,
                    from include/linux/time.h:60,
                    from include/linux/stat.h:19,
                    from include/linux/module.h:13,
                    from kernel/trace/trace_events_hist.c:8:
   In function 'strncat',
       inlined from 'last_cmd_set' at kernel/trace/trace_events_hist.c:760:2,
       inlined from 'event_hist_trigger_parse' at kernel/trace/trace_events_hist.c:6191:3:
>> include/linux/fortify-string.h:47:30: warning: '__builtin_strncat' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
      47 | #define __underlying_strncat __builtin_strncat
         |                              ^
   include/linux/fortify-string.h:191:10: note: in expansion of macro '__underlying_strncat'
     191 |   return __underlying_strncat(p, q, count);
         |          ^~~~~~~~~~~~~~~~~~~~
   kernel/trace/trace_events_hist.c: In function 'event_hist_trigger_parse':
   include/linux/fortify-string.h:46:29: note: length computed here
      46 | #define __underlying_strlen __builtin_strlen
         |                             ^
   include/linux/fortify-string.h:102:10: note: in expansion of macro '__underlying_strlen'
     102 |   return __underlying_strlen(p);
         |          ^~~~~~~~~~~~~~~~~~~


vim +/__builtin_strncat +47 include/linux/fortify-string.h

3009f891bb9f32 Kees Cook      2021-08-02  26  
a28a6e860c6cf2 Francis Laniel 2021-02-25  27  #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
a28a6e860c6cf2 Francis Laniel 2021-02-25  28  extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr);
a28a6e860c6cf2 Francis Laniel 2021-02-25  29  extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp);
a28a6e860c6cf2 Francis Laniel 2021-02-25  30  extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy);
a28a6e860c6cf2 Francis Laniel 2021-02-25  31  extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove);
a28a6e860c6cf2 Francis Laniel 2021-02-25  32  extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset);
a28a6e860c6cf2 Francis Laniel 2021-02-25  33  extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat);
a28a6e860c6cf2 Francis Laniel 2021-02-25  34  extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy);
a28a6e860c6cf2 Francis Laniel 2021-02-25  35  extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen);
a28a6e860c6cf2 Francis Laniel 2021-02-25  36  extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat);
a28a6e860c6cf2 Francis Laniel 2021-02-25  37  extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy);
a28a6e860c6cf2 Francis Laniel 2021-02-25  38  #else
a28a6e860c6cf2 Francis Laniel 2021-02-25  39  #define __underlying_memchr	__builtin_memchr
a28a6e860c6cf2 Francis Laniel 2021-02-25  40  #define __underlying_memcmp	__builtin_memcmp
a28a6e860c6cf2 Francis Laniel 2021-02-25  41  #define __underlying_memcpy	__builtin_memcpy
a28a6e860c6cf2 Francis Laniel 2021-02-25  42  #define __underlying_memmove	__builtin_memmove
a28a6e860c6cf2 Francis Laniel 2021-02-25  43  #define __underlying_memset	__builtin_memset
a28a6e860c6cf2 Francis Laniel 2021-02-25  44  #define __underlying_strcat	__builtin_strcat
a28a6e860c6cf2 Francis Laniel 2021-02-25  45  #define __underlying_strcpy	__builtin_strcpy
a28a6e860c6cf2 Francis Laniel 2021-02-25  46  #define __underlying_strlen	__builtin_strlen
a28a6e860c6cf2 Francis Laniel 2021-02-25 @47  #define __underlying_strncat	__builtin_strncat
a28a6e860c6cf2 Francis Laniel 2021-02-25  48  #define __underlying_strncpy	__builtin_strncpy
a28a6e860c6cf2 Francis Laniel 2021-02-25  49  #endif
a28a6e860c6cf2 Francis Laniel 2021-02-25  50  

:::::: The code at line 47 was first introduced by commit
:::::: a28a6e860c6cf231cf3c5171c75c342adcd00406 string.h: move fortified functions definitions in a dedicated header.

:::::: TO: Francis Laniel <laniel_francis@xxxxxxxxxxxxxxxxxxx>
:::::: CC: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>

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