kasan: fix array-bounds warnings in tests

GCC's -Warray-bounds option detects out-of-bounds accesses to
statically-sized allocations in krealloc out-of-bounds tests.

Use OPTIMIZER_HIDE_VAR to suppress the warning.

Also change kmalloc_memmove_invalid_size to use OPTIMIZER_HIDE_VAR
instead of a volatile variable.

Link: https://lkml.kernel.org/r/e94399242d32e00bba6fd0d9ec4c897f188128e8.1664215688.git.andreyknvl@google.com
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reported-by: kernel test robot <lkp@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index f25692d..57e4c72 100644 (file)
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -295,6 +295,9 @@ static void krealloc_more_oob_helper(struct kunit *test,
        ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
 
+       /* Suppress -Warray-bounds warnings. */
+       OPTIMIZER_HIDE_VAR(ptr2);
+
        /* All offsets up to size2 must be accessible. */
        ptr2[size1 - 1] = 'x';
        ptr2[size1] = 'x';
@@ -327,6 +330,9 @@ static void krealloc_less_oob_helper(struct kunit *test,
        ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
 
+       /* Suppress -Warray-bounds warnings. */
+       OPTIMIZER_HIDE_VAR(ptr2);
+
        /* Must be accessible for all modes. */
        ptr2[size2 - 1] = 'x';
 
@@ -540,13 +546,14 @@ static void kmalloc_memmove_invalid_size(struct kunit *test)
 {
        char *ptr;
        size_t size = 64;
-       volatile size_t invalid_size = size;
+       size_t invalid_size = size;
 
        ptr = kmalloc(size, GFP_KERNEL);
        KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
        memset((char *)ptr, 0, 64);
        OPTIMIZER_HIDE_VAR(ptr);
+       OPTIMIZER_HIDE_VAR(invalid_size);
        KUNIT_EXPECT_KASAN_FAIL(test,
                memmove((char *)ptr, (char *)ptr + 4, invalid_size));
        kfree(ptr);