From: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Rework kmalloc_oob_right() to do these bad access checks:
1. An unaligned access one byte past the requested kmalloc size
(can only be detected by KASAN_GENERIC).
2. An aligned access into the first out-of-bounds granule that falls
within the aligned kmalloc object.
3. Out-of-bounds access past the aligned kmalloc object.
Test #3 deliberately uses a read access to avoid corrupting memory.
Otherwise, this test might lead to crashes with the HW_TAGS mode, as it
neither uses quarantine nor redzones.
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
---
lib/test_kasan.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 8f7b0b2f6e11..1bc3cdd2957f 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -122,12 +122,28 @@ static void kasan_test_exit(struct kunit *test)
static void kmalloc_oob_right(struct kunit *test)
{
char *ptr;
- size_t size = 123;
+ size_t size = 128 - KASAN_GRANULE_SIZE - 5;
ptr = kmalloc(size, GFP_KERNEL);
KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
- KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 'x');
+ /*
+ * An unaligned access past the requested kmalloc size.
+ * Only generic KASAN can precisely detect these.
+ */
+ if (IS_ENABLED(CONFIG_KASAN_GENERIC))
+ KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 'x');
+
+ /*
+ * An aligned access into the first out-of-bounds granule that falls
+ * within the aligned kmalloc object.
+ */
+ KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + 5] = 'y');
+
+ /* Out-of-bounds access past the aligned kmalloc object. */
+ KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] =
+ ptr[size + KASAN_GRANULE_SIZE + 5]);
+
kfree(ptr);
}
--
2.25.1
