Re: [PATCH v2 14/16] kasan: Remove ksize()-related tests
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2022-09-24 08:18:13
Also in:
dri-devel, intel-wired-lan, linux-btrfs, linux-fsdevel, linux-hardening, linux-media, linux-mm, lkml, llvm
On Fri, 23 Sept 2022 at 22:28, Kees Cook [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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'; I would rather keep the tests and update to the new behavior. We had bugs in ksize, we need test coverage. I assume ptr[size] access must now produce an error even after ksize.
- /* 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));This is still a bug that should be detected, right? Calling ksize on a freed pointer is a bug.
quoted hunk ↗ jump to hunk
- 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