[PATCH v2 14/16] kasan: Remove ksize()-related tests

Kees Cook
2022-09-23T20:35:37Z

In preparation for no longer unpoisoning in ksize(), remove the behavioral
self-tests for ksize().

Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: kasan-dev@googlegroups.com
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
lib/test_kasan.c | 42 ------------------------------------------
mm/kasan/shadow.c | 4 +---
2 files changed, 1 insertion(+), 45 deletions(-)

diff --git a/lib/test_kasan.c b/lib/test_kasan.c
index 58c1b01ccfe2..bdd0ced8f8d7 100644
--- a/lib/test_kasan.c
+++ b/lib/test_kasan.c
@@ -753,46 +753,6 @@ static void kasan_global_oob_left(struct kunit *test)
KUNIT_EXPECT_KASAN_FAIL(test, *(volatile char *)p);
}

-/* Check that ksize() makes the whole object accessible. */
-static void ksize_unpoisons_memory(struct kunit *test)
-{
- char *ptr;
- size_t size = 123, real_size;
-
- ptr = kmalloc(size, GFP_KERNEL);
- KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
- real_size = ksize(ptr);
-
- OPTIMIZER_HIDE_VAR(ptr);
-
- /* This access shouldn't trigger a KASAN report. */
- ptr[size] = 'x';
-
- /* This one must. */
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[real_size]);
-
- kfree(ptr);
-}
-
-/*
- * Check that a use-after-free is detected by ksize() and via normal accesses
- * after it.
- */
-static void ksize_uaf(struct kunit *test)
-{
- char *ptr;
- int size = 128 - KASAN_GRANULE_SIZE;
-
- ptr = kmalloc(size, GFP_KERNEL);
- KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
- kfree(ptr);
-
- OPTIMIZER_HIDE_VAR(ptr);
- KUNIT_EXPECT_KASAN_FAIL(test, ksize(ptr));
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[0]);
- KUNIT_EXPECT_KASAN_FAIL(test, ((volatile char *)ptr)[size]);
-}
-
static void kasan_stack_oob(struct kunit *test)
{
char stack_array[10];
@@ -1392,8 +1352,6 @@ static struct kunit_case kasan_kunit_test_cases[] = {
KUNIT_CASE(kasan_stack_oob),
KUNIT_CASE(kasan_alloca_oob_left),
KUNIT_CASE(kasan_alloca_oob_right),
- KUNIT_CASE(ksize_unpoisons_memory),
- KUNIT_CASE(ksize_uaf),
KUNIT_CASE(kmem_cache_double_free),
KUNIT_CASE(kmem_cache_invalid_free),
KUNIT_CASE(kmem_cache_double_destroy),
diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 0e3648b603a6..0895c73e9b69 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c
@@ -124,9 +124,7 @@ void kasan_unpoison(const void *addr, size_t size, bool init)
addr = kasan_reset_tag(addr);

/*
- * Skip KFENCE memory if called explicitly outside of sl*b. Also note
- * that calls to ksize(), where size is not a multiple of machine-word
- * size, would otherwise poison the invalid portion of the word.
+ * Skip KFENCE memory if called explicitly outside of sl*b.
*/
if (is_kfence_address(addr))
return;
--
2.34.1