Re: [PATCH v2] kconfig: fix potential NULL pointer dereference in conf_askvalue()

[kernel test robot <lkp@intel.com>]

Hi Xingjing,

kernel test robot noticed the following build errors:

[auto build test ERROR on linus/master]
[also build test ERROR on v7.0-rc1 next-20260227]
[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#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Xingjing-Deng/kconfig-fix-potential-NULL-pointer-dereference-in-conf_askvalue/20260301-133159
base:   linus/master
patch link:    https://lore.kernel.org/r/20260301053035.1950087-1-micro6947%40gmail.com
patch subject: [PATCH v2] kconfig: fix potential NULL pointer dereference in conf_askvalue()
config: x86_64-rhel-9.4 (attached as .config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260302/202603020347.rhUXW6ql-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/202603020347.rhUXW6ql-lkp@intel.com/

All errors (new ones prefixed by >>):

   scripts/kconfig/conf.c: In function 'conf_askvalue':
>> scripts/kconfig/conf.c:300:35: error: expected ')' before ':' token
     300 |                 printf("%s\n", def :? "");
         |                       ~           ^~
         |                                   )
   scripts/kconfig/conf.c:308:43: error: expected ')' before ':' token
     308 |                         printf("%s\n", def :? "");
         |                               ~           ^~
         |                                           )
   make[3]: *** [scripts/Makefile.host:131: scripts/kconfig/conf.o] Error 1
   make[3]: Target 'oldconfig' not remade because of errors.
   make[2]: *** [Makefile:746: oldconfig] Error 2
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'oldconfig' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'oldconfig' not remade because of errors.
--
   scripts/kconfig/conf.c: In function 'conf_askvalue':
>> scripts/kconfig/conf.c:300:35: error: expected ')' before ':' token
     300 |                 printf("%s\n", def :? "");
         |                       ~           ^~
         |                                   )
   scripts/kconfig/conf.c:308:43: error: expected ')' before ':' token
     308 |                         printf("%s\n", def :? "");
         |                               ~           ^~
         |                                           )
   make[3]: *** [scripts/Makefile.host:131: scripts/kconfig/conf.o] Error 1
   make[3]: Target 'olddefconfig' not remade because of errors.
   make[2]: *** [Makefile:746: olddefconfig] Error 2
   make[1]: *** [Makefile:248: __sub-make] Error 2
   make[1]: Target 'olddefconfig' not remade because of errors.
   make: *** [Makefile:248: __sub-make] Error 2
   make: Target 'olddefconfig' not remade because of errors.


vim +300 scripts/kconfig/conf.c

   290	
   291	static int conf_askvalue(struct symbol *sym, const char *def)
   292	{
   293		if (!sym_has_value(sym))
   294			printf("(NEW) ");
   295	
   296		line[0] = '\n';
   297		line[1] = 0;
   298	
   299		if (!sym_is_changeable(sym)) {
 > 300			printf("%s\n", def :? "");
   301			return 0;
   302		}
   303	
   304		switch (input_mode) {
   305		case oldconfig:
   306		case syncconfig:
   307			if (sym_has_value(sym)) {
   308				printf("%s\n", def :? "");
   309				return 0;
   310			}
   311			/* fall through */
   312		default:
   313			fflush(stdout);
   314			xfgets(line, sizeof(line), stdin);
   315			break;
   316		}
   317	
   318		return 1;
   319	}
   320	

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