Re: [PATCH fs/bfs 1/2] bfs: fix null-ptr-deref in bfs_move_block

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

Hi,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.10-rc7 next-20240711]
[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/kovalev-altlinux-org/bfs-fix-null-ptr-deref-in-bfs_move_block/20240711-072644
base:   linus/master
patch link:    https://lore.kernel.org/r/20240710191118.40431-2-kovalev%40altlinux.org
patch subject: [PATCH fs/bfs 1/2] bfs: fix null-ptr-deref in bfs_move_block
config: arm-randconfig-001-20240711 (https://download.01.org/0day-ci/archive/20240712/202407120052.Al11h5ur-lkp@intel.com/config)
compiler: clang version 19.0.0git (https://github.com/llvm/llvm-project a0c6b8aef853eedaa0980f07c0a502a5a8a9740e)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240712/202407120052.Al11h5ur-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/202407120052.Al11h5ur-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from fs/bfs/file.c:15:
   In file included from include/linux/buffer_head.h:12:
   In file included from include/linux/blk_types.h:10:
   In file included from include/linux/bvec.h:10:
   In file included from include/linux/highmem.h:8:
   In file included from include/linux/cacheflush.h:5:
   In file included from arch/arm/include/asm/cacheflush.h:10:
   In file included from include/linux/mm.h:2258:
   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/bfs/file.c:44:6: warning: variable 'err' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
      44 |         if (unlikely(!new)) {
         |             ^~~~~~~~~~~~~~
   include/linux/compiler.h:77:22: note: expanded from macro 'unlikely'
      77 | # define unlikely(x)    __builtin_expect(!!(x), 0)
         |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~
   fs/bfs/file.c:53:9: note: uninitialized use occurs here
      53 |         return err;
         |                ^~~
   fs/bfs/file.c:44:2: note: remove the 'if' if its condition is always true
      44 |         if (unlikely(!new)) {
         |         ^~~~~~~~~~~~~~~~~~~
   fs/bfs/file.c:38:9: note: initialize the variable 'err' to silence this warning
      38 |         int err;
         |                ^
         |                 = 0
   2 warnings generated.


vim +44 fs/bfs/file.c

    33	
    34	static int bfs_move_block(unsigned long from, unsigned long to,
    35						struct super_block *sb)
    36	{
    37		struct buffer_head *bh, *new;
    38		int err;
    39	
    40		bh = sb_bread(sb, from);
    41		if (!bh)
    42			return -EIO;
    43		new = sb_getblk(sb, to);
  > 44		if (unlikely(!new)) {
    45			err = -EIO;
    46			goto out_err_new;
    47		}
    48		memcpy(new->b_data, bh->b_data, bh->b_size);
    49		mark_buffer_dirty(new);
    50		brelse(new);
    51	out_err_new:
    52		bforget(bh);
    53		return err;
    54	}
    55	

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