Re: [PATCH v3 1/3] x86/mce: Use is_copy_from_user() to determine copy-from-user context

[kernel test robot]

Hi Shuai,

kernel test robot noticed the following build errors:

[auto build test ERROR on akpm-mm/mm-everything]

url:    https://github.com/intel-lab-lkp/linux/commits/Shuai-Xue/x86-mce-Use-is_copy_from_user-to-determine-copy-from-user-context/20250306-101505
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20250306021031.5538-2-xueshuai%40linux.alibaba.com
patch subject: [PATCH v3 1/3] x86/mce: Use is_copy_from_user() to determine copy-from-user context
config: i386-buildonly-randconfig-002-20250307 (https://download.01.org/0day-ci/archive/20250307/202503071154.xQpKARjN-lkp@xxxxxxxxx/config)
compiler: clang version 19.1.7 (https://github.com/llvm/llvm-project cd708029e0b2869e80abe31ddb175f7c35361f90)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250307/202503071154.xQpKARjN-lkp@xxxxxxxxx/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@xxxxxxxxx>
| Closes: https://lore.kernel.org/oe-kbuild-all/202503071154.xQpKARjN-lkp@xxxxxxxxx/

All errors (new ones prefixed by >>):

   In file included from arch/x86/kernel/cpu/mce/severity.c:16:
   In file included from arch/x86/include/asm/traps.h:6:
   In file included from include/linux/kprobes.h:28:
   In file included from include/linux/ftrace.h:13:
   In file included from include/linux/kallsyms.h:13:
   In file included from include/linux/mm.h:2321:
   include/linux/vmstat.h:518:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     518 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> arch/x86/kernel/cpu/mce/severity.c:305:25: error: expected ';' after return statement
     305 |                 return IN_KERNEL_RECOV
         |                                       ^
         |                                       ;
   1 warning and 1 error generated.


vim +305 arch/x86/kernel/cpu/mce/severity.c

   274	
   275	/*
   276	 * If mcgstatus indicated that ip/cs on the stack were
   277	 * no good, then "m->cs" will be zero and we will have
   278	 * to assume the worst case (IN_KERNEL) as we actually
   279	 * have no idea what we were executing when the machine
   280	 * check hit.
   281	 * If we do have a good "m->cs" (or a faked one in the
   282	 * case we were executing in VM86 mode) we can use it to
   283	 * distinguish an exception taken in user from from one
   284	 * taken in the kernel.
   285	 */
   286	static noinstr int error_context(struct mce *m, struct pt_regs *regs)
   287	{
   288		int fixup_type;
   289		bool copy_user;
   290	
   291		if ((m->cs & 3) == 3)
   292			return IN_USER;
   293	
   294		if (!mc_recoverable(m->mcgstatus))
   295			return IN_KERNEL;
   296	
   297		/* Allow instrumentation around external facilities usage. */
   298		instrumentation_begin();
   299		fixup_type = ex_get_fixup_type(m->ip);
   300		copy_user  = is_copy_from_user(regs);
   301		instrumentation_end();
   302	
   303		if (copy_user) {
   304			m->kflags |= MCE_IN_KERNEL_COPYIN | MCE_IN_KERNEL_COPYIN;
 > 305			return IN_KERNEL_RECOV
   306		}
   307	
   308		switch (fixup_type) {
   309		case EX_TYPE_FAULT_MCE_SAFE:
   310		case EX_TYPE_DEFAULT_MCE_SAFE:
   311			m->kflags |= MCE_IN_KERNEL_RECOV;
   312			return IN_KERNEL_RECOV;
   313	
   314		default:
   315			return IN_KERNEL;
   316		}
   317	}
   318	

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