Re: [PATCH 1/2] mm/madvise: introduce PR_MADV_SELF flag to process_madvise()

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

Hi Lorenzo,

kernel test robot noticed the following build warnings:

[auto build test WARNING on akpm-mm/mm-everything]
[also build test WARNING on arnd-asm-generic/master soc/for-next linus/master v6.11 next-20240923]
[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/Lorenzo-Stoakes/mm-madvise-introduce-PR_MADV_SELF-flag-to-process_madvise/20240924-000845
base:   https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
patch link:    https://lore.kernel.org/r/077be0d59cb1047870a84c87c62e7b027af1c75d.1727106751.git.lorenzo.stoakes%40oracle.com
patch subject: [PATCH 1/2] mm/madvise: introduce PR_MADV_SELF flag to process_madvise()
config: arm-aspeed_g4_defconfig (https://download.01.org/0day-ci/archive/20240924/202409240527.pAgR35QJ-lkp@intel.com/config)
compiler: clang version 20.0.0git (https://github.com/llvm/llvm-project 8663a75fa2f31299ab8d1d90288d9df92aadee88)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240924/202409240527.pAgR35QJ-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/202409240527.pAgR35QJ-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from mm/madvise.c:9:
   In file included from include/linux/mman.h:5:
   In file included from include/linux/mm.h:2198:
   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_"
         |                               ~~~~~~~~~~~ ^ ~~~
   In file included from mm/madvise.c:21:
   include/linux/mm_inline.h:47:41: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
      47 |         __mod_lruvec_state(lruvec, NR_LRU_BASE + lru, nr_pages);
         |                                    ~~~~~~~~~~~ ^ ~~~
   include/linux/mm_inline.h:49:22: warning: arithmetic between different enumeration types ('enum zone_stat_item' and 'enum lru_list') [-Wenum-enum-conversion]
      49 |                                 NR_ZONE_LRU_BASE + lru, nr_pages);
         |                                 ~~~~~~~~~~~~~~~~ ^ ~~~
>> mm/madvise.c:1542:6: warning: variable 'mm' is uninitialized when used here [-Wuninitialized]
    1542 |         if (mm != current->mm && !process_madvise_remote_valid(behavior)) {
         |             ^~
   mm/madvise.c:1511:22: note: initialize the variable 'mm' to silence this warning
    1511 |         struct mm_struct *mm;
         |                             ^
         |                              = NULL
   4 warnings generated.


vim +/mm +1542 mm/madvise.c

  1502	
  1503	SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec,
  1504			size_t, vlen, int, behavior, unsigned int, flags)
  1505	{
  1506		ssize_t ret;
  1507		struct iovec iovstack[UIO_FASTIOV];
  1508		struct iovec *iov = iovstack;
  1509		struct iov_iter iter;
  1510		struct task_struct *task;
  1511		struct mm_struct *mm;
  1512		unsigned int f_flags;
  1513	
  1514		if (flags & ~PR_MADV_SELF) {
  1515			ret = -EINVAL;
  1516			goto out;
  1517		}
  1518	
  1519		ret = import_iovec(ITER_DEST, vec, vlen, ARRAY_SIZE(iovstack), &iov, &iter);
  1520		if (ret < 0)
  1521			goto out;
  1522	
  1523		/*
  1524		 * Perform an madvise operation on the current process. No restrictions
  1525		 * need be applied, nor do we need to pin the task or mm_struct.
  1526		 */
  1527		if (flags & PR_MADV_SELF) {
  1528			ret = vector_madvise(current->mm, &iter, behavior);
  1529			goto free_iov;
  1530		}
  1531	
  1532		task = pidfd_get_task(pidfd, &f_flags);
  1533		if (IS_ERR(task)) {
  1534			ret = PTR_ERR(task);
  1535			goto free_iov;
  1536		}
  1537	
  1538		/*
  1539		 * We need only perform this check if we are attempting to manipulate a
  1540		 * remote process's address space.
  1541		 */
> 1542		if (mm != current->mm && !process_madvise_remote_valid(behavior)) {

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