From: Kees Cook <keesc...@chromium.org>

commit cab71f7495f7aa639ca4b8508f4c3e426e9cb2f7 upstream.

As done in commit d73dad4eb5ad ("kasan: test: bypass __alloc_size
checks") for __write_overflow warnings, also silence some more cases
that trip the __read_overflow warnings seen in 5.16-rc1[1]:

  In file included from include/linux/string.h:253,
                   from include/linux/bitmap.h:10,
                   from include/linux/cpumask.h:12,
                   from include/linux/mm_types_task.h:14,
                   from include/linux/mm_types.h:5,
                   from include/linux/page-flags.h:13,
                   from arch/arm64/include/asm/mte.h:14,
                   from arch/arm64/include/asm/pgtable.h:12,
                   from include/linux/pgtable.h:6,
                   from include/linux/kasan.h:29,
                   from lib/test_kasan.c:10:
  In function 'memcmp',
      inlined from 'kasan_memcmp' at lib/test_kasan.c:897:2:
  include/linux/fortify-string.h:263:25: error: call to '__read_overflow' 
declared with attribute error: detected read beyond size of object (1st 
parameter)
    263 |                         __read_overflow();
        |                         ^~~~~~~~~~~~~~~~~
  In function 'memchr',
      inlined from 'kasan_memchr' at lib/test_kasan.c:872:2:
  include/linux/fortify-string.h:277:17: error: call to '__read_overflow' 
declared with attribute error: detected read beyond size of object (1st 
parameter)
    277 |                 __read_overflow();
        |                 ^~~~~~~~~~~~~~~~~

[1] http://kisskb.ellerman.id.au/kisskb/buildresult/14660585/log/

Link: https://lkml.kernel.org/r/20211116004111.3171781-1-keesc...@chromium.org
Fixes: d73dad4eb5ad ("kasan: test: bypass __alloc_size checks")
Signed-off-by: Kees Cook <keesc...@chromium.org>
Reviewed-by: Andrey Konovalov <andreyk...@gmail.com>
Acked-by: Marco Elver <el...@google.com>
Cc: Andrey Ryabinin <ryabinin....@gmail.com>
Cc: Alexander Potapenko <gli...@google.com>
Cc: Dmitry Vyukov <dvyu...@google.com>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
Signed-off-by: Linus Torvalds <torva...@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortma...@windriver.com>
---
 lib/test_kasan.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 5475fe396ff7..de300ab98096 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -869,6 +869,7 @@ static void kasan_memchr(struct kunit *test)
        ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test,
                kasan_ptr_result = memchr(ptr, '1', size + 1));
 
@@ -894,6 +895,7 @@ static void kasan_memcmp(struct kunit *test)
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
        memset(arr, 0, sizeof(arr));
 
+       OPTIMIZER_HIDE_VAR(size);
        KUNIT_EXPECT_KASAN_FAIL(test,
                kasan_int_result = memcmp(ptr, arr, size+1));
        kfree(ptr);
-- 
2.17.1

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