linux-kernel - net/ceph/osdmap.c:1246:10: warning: result of comparison of constant 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is always false

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Message-ID: <202311060702.EjNPjAwj-lkp@intel.com>
Date:   Mon, 6 Nov 2023 07:28:38 +0800
From:   kernel test robot <lkp@...el.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
        linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>
Subject: net/ceph/osdmap.c:1246:10: warning: result of comparison of constant
 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is
 always false

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head:   77fa2fbe87fc605c4bfa87dff87be9bfded0e9a3
commit: afe956c577b2d5a3d9834e4424587c1ebcf90c4c kbuild: Enable -Wtautological-compare
date:   3 years, 7 months ago
config: x86_64-randconfig-012-20230909 (https://download.01.org/0day-ci/archive/20231106/202311060702.EjNPjAwj-lkp@intel.com/config)
compiler: clang version 16.0.4 (https://github.com/llvm/llvm-project.git ae42196bc493ffe877a7e3dff8be32035dea4d07)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231106/202311060702.EjNPjAwj-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202311060702.EjNPjAwj-lkp@intel.com/

All warnings (new ones prefixed by >>):

   net/ceph/osdmap.c:176:6: warning: no previous prototype for function 'clear_choose_args' [-Wmissing-prototypes]
   void clear_choose_args(struct crush_map *c)
        ^
   net/ceph/osdmap.c:176:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   void clear_choose_args(struct crush_map *c)
   ^
   static 
>> net/ceph/osdmap.c:1246:10: warning: result of comparison of constant 4611686018427387891 with expression of type 'u32' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
           if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
               ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   net/ceph/osdmap.c:1429:10: warning: result of comparison of constant 2305843009213693945 with expression of type 'u32' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
           if (len > (SIZE_MAX - sizeof(*pg)) / (2 * sizeof(u32)))
               ~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   3 warnings generated.
--
>> drivers/block/rbd.c:6190:17: warning: result of comparison of constant 2305843009213693948 with expression of type 'u32' (aka 'unsigned int') is always false [-Wtautological-constant-out-of-range-compare]
           if (snap_count > (SIZE_MAX - sizeof (struct ceph_snap_context))
               ~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   1 warning generated.


vim +1246 net/ceph/osdmap.c

10db634e2083a2 Ilya Dryomov 2014-03-21  1236  
a303bb0e58345f Ilya Dryomov 2017-06-21  1237  static struct ceph_pg_mapping *__decode_pg_temp(void **p, void *end,
a303bb0e58345f Ilya Dryomov 2017-06-21  1238  						bool incremental)
a303bb0e58345f Ilya Dryomov 2017-06-21  1239  {
a303bb0e58345f Ilya Dryomov 2017-06-21  1240  	struct ceph_pg_mapping *pg;
a303bb0e58345f Ilya Dryomov 2017-06-21  1241  	u32 len, i;
a303bb0e58345f Ilya Dryomov 2017-06-21  1242  
a303bb0e58345f Ilya Dryomov 2017-06-21  1243  	ceph_decode_32_safe(p, end, len, e_inval);
a303bb0e58345f Ilya Dryomov 2017-06-21  1244  	if (len == 0 && incremental)
a303bb0e58345f Ilya Dryomov 2017-06-21  1245  		return NULL;	/* new_pg_temp: [] to remove */
a303bb0e58345f Ilya Dryomov 2017-06-21 @1246  	if (len > (SIZE_MAX - sizeof(*pg)) / sizeof(u32))
a303bb0e58345f Ilya Dryomov 2017-06-21  1247  		return ERR_PTR(-EINVAL);
a303bb0e58345f Ilya Dryomov 2017-06-21  1248  
a303bb0e58345f Ilya Dryomov 2017-06-21  1249  	ceph_decode_need(p, end, len * sizeof(u32), e_inval);
a303bb0e58345f Ilya Dryomov 2017-06-21  1250  	pg = alloc_pg_mapping(len * sizeof(u32));
10db634e2083a2 Ilya Dryomov 2014-03-21  1251  	if (!pg)
a303bb0e58345f Ilya Dryomov 2017-06-21  1252  		return ERR_PTR(-ENOMEM);
10db634e2083a2 Ilya Dryomov 2014-03-21  1253  
35a935d75d51ab Ilya Dryomov 2014-03-21  1254  	pg->pg_temp.len = len;
10db634e2083a2 Ilya Dryomov 2014-03-21  1255  	for (i = 0; i < len; i++)
35a935d75d51ab Ilya Dryomov 2014-03-21  1256  		pg->pg_temp.osds[i] = ceph_decode_32(p);
10db634e2083a2 Ilya Dryomov 2014-03-21  1257  
a303bb0e58345f Ilya Dryomov 2017-06-21  1258  	return pg;
10db634e2083a2 Ilya Dryomov 2014-03-21  1259  
10db634e2083a2 Ilya Dryomov 2014-03-21  1260  e_inval:
a303bb0e58345f Ilya Dryomov 2017-06-21  1261  	return ERR_PTR(-EINVAL);
10db634e2083a2 Ilya Dryomov 2014-03-21  1262  }
10db634e2083a2 Ilya Dryomov 2014-03-21  1263  

:::::: The code at line 1246 was first introduced by commit
:::::: a303bb0e58345fe9f7ab2f82b90266f2b5036058 libceph: introduce and switch to decode_pg_mapping()

:::::: TO: Ilya Dryomov <idryomov@...il.com>
:::::: CC: Ilya Dryomov <idryomov@...il.com>

-- 
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https://github.com/intel/lkp-tests/wiki