Re: kasan: add KUnit tests for __counted_by and __counted_by_ptr

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

Hi Bill,

kernel test robot noticed the following build warnings:



url:    https://github.com/intel-lab-lkp/linux/commits/Bill-Wendling/kasan-add-KUnit-tests-for-__counted_by-and-__counted_by_ptr/20260928-231737
base:   
patch link:    https://lore.kernel.org/r/202609302227.ZAhd0ZIv-lkp%40intel.com
config: x86_64-randconfig-2300-20260930 (https://download.01.org/0day-ci/archive/20260930/202609302227.ZAhd0ZIv-lkp@intel.com/config)
compiler: clang version 22.1.8 (https://github.com/llvm/llvm-project ca7933e47d3a3451d81e72ac174dcb5aa28b59d1)
sparse: v0.6.5-rc1
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260930/202609302227.ZAhd0ZIv-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/202609302227.ZAhd0ZIv-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
   mm/kasan/kasan_test_c.c:1598:27: sparse: sparse: Variable length array is used.
   mm/kasan/kasan_test_c.c:1613:27: sparse: sparse: Variable length array is used.
   mm/kasan/kasan_test_c.c:2237:9: sparse: sparse: undefined identifier '__builtin_dynamic_object_size'
   mm/kasan/kasan_test_c.c:2237:9: sparse: sparse: undefined identifier '__builtin_dynamic_object_size'
>> mm/kasan/kasan_test_c.c:2237:9: sparse: sparse: incompatible types for operation (==):
   mm/kasan/kasan_test_c.c:2237:9: sparse:    unsigned long const __left
   mm/kasan/kasan_test_c.c:2237:9: sparse:    bad type const __right
   mm/kasan/kasan_test_c.c:2284:9: sparse: sparse: undefined identifier '__builtin_dynamic_object_size'
   mm/kasan/kasan_test_c.c:2284:9: sparse: sparse: undefined identifier '__builtin_dynamic_object_size'
   mm/kasan/kasan_test_c.c:2284:9: sparse: sparse: incompatible types for operation (==):
   mm/kasan/kasan_test_c.c:2284:9: sparse:    unsigned long const __left
   mm/kasan/kasan_test_c.c:2284:9: sparse:    bad type const __right

vim +2237 mm/kasan/kasan_test_c.c

  2226	
  2227	static void counted_by_flex_oob_access(struct kunit *test)
  2228	{
  2229		size_t size = 128;
  2230		struct counted_by_flex_struct *s;
  2231	
  2232		s = alloc_counted_by_flex_struct(test, size);
  2233	
  2234		OPTIMIZER_HIDE_VAR(s);
  2235	
  2236		/* __builtin_dynamic_object_size() should return the correct length. */
> 2237		KUNIT_EXPECT_EQ(test, size * sizeof(s->array[0]),
  2238				__builtin_dynamic_object_size(s->array, 0));
  2239	
  2240		/* Out-of-bounds assignment. */
  2241		KUNIT_EXPECT_KASAN_FAIL(test, s->array[size + 1] = 42);
  2242	
  2243		/* Out-of-bounds read. */
  2244		KUNIT_EXPECT_KASAN_FAIL_READ(test, s->array[0] = s->array[size + 13]);
  2245	
  2246		kfree(s);
  2247	}
  2248	

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