Re: [PATCH v2 1/2] mm/ksm: fix ksm exec support for prctl

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

Hi Jinjiang,

kernel test robot noticed the following build warnings:

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

url:    https://github.com/intel-lab-lkp/linux/commits/Jinjiang-Tu/mm-ksm-fix-ksm-exec-support-for-prctl/20240322-141317
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/20240322060947.3254967-2-tujinjiang%40huawei.com
patch subject: [PATCH v2 1/2] mm/ksm: fix ksm exec support for prctl
config: s390-allnoconfig (https://download.01.org/0day-ci/archive/20240324/202403240716.8B7CiDbr-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project 23de3862dce582ce91c1aa914467d982cb1a73b4)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240324/202403240716.8B7CiDbr-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/202403240716.8B7CiDbr-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from fs/exec.c:30:
   In file included from include/linux/mm.h:2211:
   include/linux/vmstat.h:514:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
     514 |         return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_"
         |                               ~~~~~~~~~~~ ^ ~~~
>> fs/exec.c:275:6: warning: variable 'err' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized]
     275 |         if (ksm_execve(mm))
         |             ^~~~~~~~~~~~~~
   fs/exec.c:305:9: note: uninitialized use occurs here
     305 |         return err;
         |                ^~~
   fs/exec.c:275:2: note: remove the 'if' if its condition is always false
     275 |         if (ksm_execve(mm))
         |         ^~~~~~~~~~~~~~~~~~~
     276 |                 goto err_ksm;
         |                 ~~~~~~~~~~~~
   fs/exec.c:257:9: note: initialize the variable 'err' to silence this warning
     257 |         int err;
         |                ^
         |                 = 0
   2 warnings generated.


vim +275 fs/exec.c

   254	
   255	static int __bprm_mm_init(struct linux_binprm *bprm)
   256	{
   257		int err;
   258		struct vm_area_struct *vma = NULL;
   259		struct mm_struct *mm = bprm->mm;
   260	
   261		bprm->vma = vma = vm_area_alloc(mm);
   262		if (!vma)
   263			return -ENOMEM;
   264		vma_set_anonymous(vma);
   265	
   266		if (mmap_write_lock_killable(mm)) {
   267			err = -EINTR;
   268			goto err_free;
   269		}
   270	
   271		/*
   272		 * Need to be called with mmap write lock
   273		 * held, to avoid race with ksmd.
   274		*/
 > 275		if (ksm_execve(mm))
   276			goto err_ksm;
   277	
   278		/*
   279		 * Place the stack at the largest stack address the architecture
   280		 * supports. Later, we'll move this to an appropriate place. We don't
   281		 * use STACK_TOP because that can depend on attributes which aren't
   282		 * configured yet.
   283		 */
   284		BUILD_BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
   285		vma->vm_end = STACK_TOP_MAX;
   286		vma->vm_start = vma->vm_end - PAGE_SIZE;
   287		vm_flags_init(vma, VM_SOFTDIRTY | VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP);
   288		vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
   289	
   290		err = insert_vm_struct(mm, vma);
   291		if (err)
   292			goto err;
   293	
   294		mm->stack_vm = mm->total_vm = 1;
   295		mmap_write_unlock(mm);
   296		bprm->p = vma->vm_end - sizeof(void *);
   297		return 0;
   298	err:
   299		ksm_exit(mm);
   300	err_ksm:
   301		mmap_write_unlock(mm);
   302	err_free:
   303		bprm->vma = NULL;
   304		vm_area_free(vma);
   305		return err;
   306	}
   307	

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