Re: drivers/base/regmap/regcache-maple.c:114:23: warning: 'upper_index' is used uninitialized

["Liu, Yujie" <yujie.liu@intel.com>]

Hi Geert,

On Tue, 2023-07-25 at 11:06 +0200, Geert Uytterhoeven wrote:
> Hi Robot,
> 
> On Tue, Jul 25, 2023 at 10:17 AM kernel test robot <lkp@intel.com> wrote:
> > FYI, the error/warning still remains.
> > 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head:   0b5547c51827e053cc754db47d3ec3e6c2c451d2
> > commit: f033c26de5a5734625d2dd1dc196745fae186f1b regmap: Add maple tree based register cache
> > date:   4 months ago
> > config: arc-randconfig-r001-20230725 (https://download.01.org/0day-ci/archive/20230725/202307251518.4JYwdU5r-lkp@intel.com/config)
> > compiler: arc-elf-gcc (GCC) 12.3.0
> > reproduce: (https://download.01.org/0day-ci/archive/20230725/202307251518.4JYwdU5r-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/202307251518.4JYwdU5r-lkp@intel.com/
> > 
> > All warnings (new ones prefixed by >>):
> > 
> >    drivers/base/regmap/regcache-maple.c: In function 'regcache_maple_drop':
> > > > drivers/base/regmap/regcache-maple.c:114:23: warning: 'upper_index' is used uninitialized [-Wuninitialized]
> >      114 |         unsigned long upper_index, upper_last;
> >          |                       ^~~~~~~~~~~
> > > > drivers/base/regmap/regcache-maple.c:114:36: warning: 'upper_last' is used uninitialized [-Wuninitialized]
> >      114 |         unsigned long upper_index, upper_last;
> >          |                                    ^~~~~~~~~~
> >    drivers/base/regmap/regcache-maple.c:113:23: warning: 'lower_index' is used uninitialized [-Wuninitialized]
> >      113 |         unsigned long lower_index, lower_last;
> >          |                       ^~~~~~~~~~~
> >    drivers/base/regmap/regcache-maple.c:113:36: warning: 'lower_last' is used uninitialized [-Wuninitialized]
> >      113 |         unsigned long lower_index, lower_last;
> >          |                                    ^~~~~~~~~~
> 
> These are false positives...

Sorry for the noise. We've configured the bot to filter out these false
positives.

Thanks,
Yujie

> > 
> > 
> > vim +/upper_index +114 drivers/base/regmap/regcache-maple.c
> > 
> >    106
> >    107  static int regcache_maple_drop(struct regmap *map, unsigned int min,
> >    108                                 unsigned int max)
> >    109  {
> >    110          struct maple_tree *mt = map->cache;
> >    111          MA_STATE(mas, mt, min, max);
> >    112          unsigned long *entry, *lower, *upper;
> >    113          unsigned long lower_index, lower_last;
> >  > 114          unsigned long upper_index, upper_last;
> >    115          int ret;
> >    116
> >    117          lower = NULL;
> >    118          upper = NULL;
> >    119
> >    120          mas_lock(&mas);
> >    121
> >    122          mas_for_each(&mas, entry, max) {
> >    123                  /*
> >    124                   * This is safe because the regmap lock means the
> >    125                   * Maple lock is redundant, but we need to take it due
> >    126                   * to lockdep asserts in the maple tree code.
> >    127                   */
> >    128                  mas_unlock(&mas);
> >    129
> >    130                  /* Do we need to save any of this entry? */
> >    131                  if (mas.index < min) {
> >    132                          lower_index = mas.index;
> >    133                          lower_last = min -1;
> >    134
> >    135                          lower = kmemdup(entry, ((min - mas.index) *
> >    136                                                  sizeof(unsigned long)),
> >    137                                          GFP_KERNEL);
> 
>  lower{,_index,_last} and ...
> 
> >    138                          if (!lower) {
> >    139                                  ret = -ENOMEM;
> >    140                                  goto out;
> >    141                          }
> >    142                  }
> >    143
> >    144                  if (mas.last > max) {
> >    145                          upper_index = max + 1;
> >    146                          upper_last = mas.last;
> >    147
> >    148                          upper = kmemdup(&entry[max + 1],
> >    149                                          ((mas.last - max) *
> >    150                                           sizeof(unsigned long)),
> >    151                                          GFP_KERNEL);
> 
> upper{,_index,_last} are always initialized together, ...
> 
> >    152                          if (!upper) {
> >    153                                  ret = -ENOMEM;
> >    154                                  goto out;
> >    155                          }
> >    156                  }
> >    157
> >    158                  kfree(entry);
> >    159                  mas_lock(&mas);
> >    160                  mas_erase(&mas);
> >    161
> >    162                  /* Insert new nodes with the saved data */
> >    163                  if (lower) {
> 
> but these gatekeepers...
> 
> >    164                          mas_set_range(&mas, lower_index, lower_last);
> >    165                          ret = mas_store_gfp(&mas, lower, GFP_KERNEL);
> >    166                          if (ret != 0)
> >    167                                  goto out;
> >    168                          lower = NULL;
> >    169                  }
> >    170
> >    171                  if (upper) {
> 
> check only one of them (which are preinitialized at lines 117/118).
> 
> >    172                          mas_set_range(&mas, upper_index, upper_last);
> >    173                          ret = mas_store_gfp(&mas, upper, GFP_KERNEL);
> >    174                          if (ret != 0)
> >    175                                  goto out;
> >    176                          upper = NULL;
> >    177                  }
> >    178          }
> >    179
> >    180  out:
> >    181          mas_unlock(&mas);
> >    182          kfree(lower);
> >    183          kfree(upper);
> >    184
> >    185          return ret;
> >    186  }
> >    187
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
>