linux-kernel - [PATCH mm v2] kasan: fix array-bounds warnings in tests

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Date:   Sat, 24 Sep 2022 22:23:21 +0200
From:   andrey.konovalov@...ux.dev
To:     Marco Elver <elver@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Andrey Konovalov <andreyknvl@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH mm v2] kasan: fix array-bounds warnings in tests

From: Andrey Konovalov <andreyknvl@...gle.com>

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.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

---

Changes v1->v2:
- Hide ptr2 instead of size1 and size2 to be consistent with other
  uses of OPTIMIZER_HIDE_VAR in KASAN tests.
---
 mm/kasan/kasan_test.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/kasan/kasan_test.c b/mm/kasan/kasan_test.c
index 71cb402c404f..dbb0a672380f 100644
--- a/mm/kasan/kasan_test.c
+++ b/mm/kasan/kasan_test.c
@@ -333,6 +333,8 @@ static void krealloc_more_oob_helper(struct kunit *test,
 	ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
 
+	OPTIMIZER_HIDE_VAR(ptr2);
+
 	/* All offsets up to size2 must be accessible. */
 	ptr2[size1 - 1] = 'x';
 	ptr2[size1] = 'x';
@@ -365,6 +367,8 @@ static void krealloc_less_oob_helper(struct kunit *test,
 	ptr2 = krealloc(ptr1, size2, GFP_KERNEL);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
 
+	OPTIMIZER_HIDE_VAR(ptr2);
+
 	/* Must be accessible for all modes. */
 	ptr2[size2 - 1] = 'x';
 
@@ -578,13 +582,14 @@ 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);
-- 
2.25.1