Re: [PATCH 11/11] kasan: add proper page allocator tests

[Marco Elver]

On Tue, Jan 05, 2021 at 07:27PM +0100, Andrey Konovalov wrote:
> The currently existing page allocator tests rely on kmalloc fallback
> with large sizes that is only present for SLUB. Add proper tests that
> use alloc/free_pages().
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> Link: https://linux-review.googlesource.com/id/Ia173d5a1b215fe6b2548d814ef0f4433cf983570

Reviewed-by: Marco Elver <elver@xxxxxxxxxx>

> ---
>  lib/test_kasan.c | 54 +++++++++++++++++++++++++++++++++++++++++++-----
>  1 file changed, 49 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/test_kasan.c b/lib/test_kasan.c
> index 6261521e57ad..24798c034d05 100644
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -128,6 +128,12 @@ static void kmalloc_node_oob_right(struct kunit *test)
>  	kfree(ptr);
>  }
>  
> +/*
> + * These kmalloc_pagealloc_* tests try allocating a memory chunk that doesn't
> + * fit into a slab cache and therefore is allocated via the page allocator
> + * fallback. Since this kind of fallback is only implemented for SLUB, these
> + * tests are limited to that allocator.
> + */
>  static void kmalloc_pagealloc_oob_right(struct kunit *test)
>  {
>  	char *ptr;
> @@ -138,14 +144,11 @@ static void kmalloc_pagealloc_oob_right(struct kunit *test)
>  		return;
>  	}
>  
> -	/*
> -	 * Allocate a chunk that does not fit into a SLUB cache to trigger
> -	 * the page allocator fallback.
> -	 */
>  	ptr = kmalloc(size, GFP_KERNEL);
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
>  
>  	KUNIT_EXPECT_KASAN_FAIL(test, ptr[size + OOB_TAG_OFF] = 0);
> +
>  	kfree(ptr);
>  }
>  
> @@ -161,8 +164,8 @@ static void kmalloc_pagealloc_uaf(struct kunit *test)
>  
>  	ptr = kmalloc(size, GFP_KERNEL);
>  	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> -
>  	kfree(ptr);
> +
>  	KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = 0);
>  }
>  
> @@ -182,6 +185,45 @@ static void kmalloc_pagealloc_invalid_free(struct kunit *test)
>  	KUNIT_EXPECT_KASAN_FAIL(test, kfree(ptr + 1));
>  }
>  
> +static void pagealloc_oob_right(struct kunit *test)
> +{
> +	char *ptr;
> +	struct page *pages;
> +	size_t order = 4;
> +	size_t size = (1UL << (PAGE_SHIFT + order));
> +
> +	/*
> +	 * With generic KASAN page allocations have no redzones, thus
> +	 * out-of-bounds detection is not guaranteed.
> +	 * See https://bugzilla.kernel.org/show_bug.cgi?id=210503.
> +	 */
> +	if (IS_ENABLED(CONFIG_KASAN_GENERIC)) {
> +		kunit_info(test, "skipping, CONFIG_KASAN_GENERIC enabled");
> +		return;
> +	}
> +
> +	pages = alloc_pages(GFP_KERNEL, order);
> +	ptr = page_address(pages);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> +
> +	KUNIT_EXPECT_KASAN_FAIL(test, ptr[size] = 0);
> +	free_pages((unsigned long)ptr, order);
> +}
> +
> +static void pagealloc_uaf(struct kunit *test)
> +{
> +	char *ptr;
> +	struct page *pages;
> +	size_t order = 4;
> +
> +	pages = alloc_pages(GFP_KERNEL, order);
> +	ptr = page_address(pages);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
> +	free_pages((unsigned long)ptr, order);
> +
> +	KUNIT_EXPECT_KASAN_FAIL(test, ptr[0] = 0);
> +}
> +
>  static void kmalloc_large_oob_right(struct kunit *test)
>  {
>  	char *ptr;
> @@ -933,6 +975,8 @@ static struct kunit_case kasan_kunit_test_cases[] = {
>  	KUNIT_CASE(kmalloc_pagealloc_oob_right),
>  	KUNIT_CASE(kmalloc_pagealloc_uaf),
>  	KUNIT_CASE(kmalloc_pagealloc_invalid_free),
> +	KUNIT_CASE(pagealloc_oob_right),
> +	KUNIT_CASE(pagealloc_uaf),
>  	KUNIT_CASE(kmalloc_large_oob_right),
>  	KUNIT_CASE(kmalloc_oob_krealloc_more),
>  	KUNIT_CASE(kmalloc_oob_krealloc_less),
> -- 
> 2.29.2.729.g45daf8777d-goog
>