[PATCH mm v3 34/34] kasan: add another use-after-free test

[andrey . konovalov]

From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Add a new use-after-free test that checks that KASAN detects use-after-free
when another object was allocated in the same slot.

This test is mainly relevant for the tag-based modes, which do not use
quarantine.

Once [1] is resolved, this test can be extended to check that the stack
traces in the report point to the proper kmalloc/kfree calls.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=212203

Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

---

Changes v2->v3:
- This is a new patch.
---
 lib/test_kasan.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 58c1b01ccfe2..505f77ffad27 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -612,6 +612,29 @@ static void kmalloc_uaf2(struct kunit *test)
 	kfree(ptr2);
 }
 
+/*
+ * Check that KASAN detects use-after-free when another object was allocated in
+ * the same slot. Relevant for the tag-based modes, which do not use quarantine.
+ */
+static void kmalloc_uaf3(struct kunit *test)
+{
+	char *ptr1, *ptr2;
+	size_t size = 100;
+
+	/* This test is specifically crafted for tag-based modes. */
+	KASAN_TEST_NEEDS_CONFIG_OFF(test, CONFIG_KASAN_GENERIC);
+
+	ptr1 = kmalloc(size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1);
+	kfree(ptr1);
+
+	ptr2 = kmalloc(size, GFP_KERNEL);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr2);
+	kfree(ptr2);
+
+	KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr1)[8]);
+}
+
 static void kfree_via_page(struct kunit *test)
 {
 	char *ptr;
@@ -1382,6 +1405,7 @@ static struct kunit_case kasan_kunit_test_cases[] = {
 	KUNIT_CASE(kmalloc_uaf),
 	KUNIT_CASE(kmalloc_uaf_memset),
 	KUNIT_CASE(kmalloc_uaf2),
+	KUNIT_CASE(kmalloc_uaf3),
 	KUNIT_CASE(kfree_via_page),
 	KUNIT_CASE(kfree_via_phys),
 	KUNIT_CASE(kmem_cache_oob),
-- 
2.25.1