[PATCH AUTOSEL 5.14 94/99] kasan: test: avoid corrupting memory via memset

Sasha Levin
2021-09-10T00:46:56Z

From: Andrey Konovalov <andreyknvl@gmail.com>

[ Upstream commit 555999a009aacd90ea51a6690e8eb2a5d0427edc ]

kmalloc_oob_memset_*() tests do writes past the allocated objects. As the
result, they corrupt memory, which might lead to crashes with the HW_TAGS
mode, as it neither uses quarantine nor redzones.

Adjust the tests to only write memory within the aligned kmalloc objects.

Also add a comment mentioning that memset tests are designed to touch both
valid and invalid memory.

Link: https://lkml.kernel.org/r/64fd457668a16e7b58d094f14a165f9d5170c5a9.1628779805.git.andreyknvl@gmail.com
Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com>
Reviewed-by: Marco Elver <elver@google.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
lib/test_kasan.c | 28 +++++++++++++++++-----------
1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index b261fe9f3110..b298edb325ab 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -412,64 +412,70 @@ static void kmalloc_uaf_16(struct kunit *test)
kfree(ptr1);
}

+/*
+ * Note: in the memset tests below, the written range touches both valid and
+ * invalid memory. This makes sure that the instrumentation does not only check
+ * the starting address but the whole range.
+ */
+
static void kmalloc_oob_memset_2(struct kunit *test)
{
char *ptr;
- size_t size = 8;
+ size_t size = 128 - KASAN_GRANULE_SIZE;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + 7 + OOB_TAG_OFF, 0, 2));
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 1, 0, 2));
kfree(ptr);
}

static void kmalloc_oob_memset_4(struct kunit *test)
{
char *ptr;
- size_t size = 8;
+ size_t size = 128 - KASAN_GRANULE_SIZE;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + 5 + OOB_TAG_OFF, 0, 4));
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 3, 0, 4));
kfree(ptr);
}

-
static void kmalloc_oob_memset_8(struct kunit *test)
{
char *ptr;
- size_t size = 8;
+ size_t size = 128 - KASAN_GRANULE_SIZE;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + 1 + OOB_TAG_OFF, 0, 8));
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 7, 0, 8));
kfree(ptr);
}

static void kmalloc_oob_memset_16(struct kunit *test)
{
char *ptr;
- size_t size = 16;
+ size_t size = 128 - KASAN_GRANULE_SIZE;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + 1 + OOB_TAG_OFF, 0, 16));
+ KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr + size - 15, 0, 16));
kfree(ptr);
}

static void kmalloc_oob_in_memset(struct kunit *test)
{
char *ptr;
- size_t size = 666;
+ size_t size = 128 - KASAN_GRANULE_SIZE;

ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);

- KUNIT_EXPECT_KASAN_FAIL(test, memset(ptr, 0, size + 5 + OOB_TAG_OFF));
+ KUNIT_EXPECT_KASAN_FAIL(test,
+ memset(ptr, 0, size + KASAN_GRANULE_SIZE));
kfree(ptr);
}

--
2.30.2