linux-hardening - Re: [PATCH] kunit: memcpy: Split slow memcpy tests into MEMCPY_SLOW_KUNIT

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Date:   Fri, 6 Jan 2023 20:36:47 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-hardening@...r.kernel.org, David Gow <davidgow@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Miguel Ojeda <ojeda@...nel.org>,
        Isabella Basso <isabbasso@...eup.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kunit: memcpy: Split slow memcpy tests into
 MEMCPY_SLOW_KUNIT_TEST

On Fri, Jan 06, 2023 at 08:02:07PM -0800, Kees Cook wrote:
> Since the long memcpy tests may stall a system for tens of seconds
> in virtualized architecture environments, split those tests off under
> CONFIG_MEMCPY_SLOW_KUNIT_TEST so they can be separately disabled.
> 
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Link: https://lore.kernel.org/lkml/20221226195206.GA2626419@roeck-us.net
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Nathan Chancellor <nathan@...nel.org>
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> Guenter, does this give you the needed flexibility to turn on the memcpy
> kunit tests again in your slower environments?

I'll be traveling this weekend. Give me until early next week to give
it a try.

Thanks,
Guenter

> ---
>  lib/Kconfig.debug  |  9 +++++++++
>  lib/memcpy_kunit.c | 17 +++++++++++++----
>  2 files changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c2c78d0e761c..b5e94807f41c 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2621,6 +2621,15 @@ config MEMCPY_KUNIT_TEST
>  
>  	  If unsure, say N.
>  
> +config MEMCPY_SLOW_KUNIT_TEST
> +	tristate "Include exhaustive memcpy tests" if !KUNIT_ALL_TESTS
> +	depends on MEMCPY_KUNIT_TEST
> +	default KUNIT_ALL_TESTS
> +	help
> +	  Some memcpy tests are quite exhaustive in checking for overlaps
> +	  and bit ranges. These can be very slow, so they are split out
> +	  as a separate config.
> +
>  config IS_SIGNED_TYPE_KUNIT_TEST
>  	tristate "Test is_signed_type() macro" if !KUNIT_ALL_TESTS
>  	depends on KUNIT
> diff --git a/lib/memcpy_kunit.c b/lib/memcpy_kunit.c
> index 89128551448d..cc1f36335a9b 100644
> --- a/lib/memcpy_kunit.c
> +++ b/lib/memcpy_kunit.c
> @@ -307,8 +307,12 @@ static void set_random_nonzero(struct kunit *test, u8 *byte)
>  	}
>  }
>  
> -static void init_large(struct kunit *test)
> +static int init_large(struct kunit *test)
>  {
> +	if (!IS_ENABLED(CONFIG_MEMCPY_SLOW_KUNIT_TEST)) {
> +		kunit_skip(test, "Slow test skipped. Enable with CONFIG_MEMCPY_SLOW_KUNIT_TEST=y");
> +		return -EBUSY;
> +	}
>  
>  	/* Get many bit patterns. */
>  	get_random_bytes(large_src, ARRAY_SIZE(large_src));
> @@ -319,6 +323,8 @@ static void init_large(struct kunit *test)
>  
>  	/* Explicitly zero the entire destination. */
>  	memset(large_dst, 0, ARRAY_SIZE(large_dst));
> +
> +	return 0;
>  }
>  
>  /*
> @@ -327,7 +333,9 @@ static void init_large(struct kunit *test)
>   */
>  static void copy_large_test(struct kunit *test, bool use_memmove)
>  {
> -	init_large(test);
> +
> +	if (init_large(test))
> +		return;
>  
>  	/* Copy a growing number of non-overlapping bytes ... */
>  	for (int bytes = 1; bytes <= ARRAY_SIZE(large_src); bytes++) {
> @@ -472,7 +480,8 @@ static void memmove_overlap_test(struct kunit *test)
>  	static const int bytes_start = 1;
>  	static const int bytes_end = ARRAY_SIZE(large_src) + 1;
>  
> -	init_large(test);
> +	if (init_large(test))
> +		return;
>  
>  	/* Copy a growing number of overlapping bytes ... */
>  	for (int bytes = bytes_start; bytes < bytes_end;
> @@ -549,8 +558,8 @@ static void strtomem_test(struct kunit *test)
>  static struct kunit_case memcpy_test_cases[] = {
>  	KUNIT_CASE(memset_test),
>  	KUNIT_CASE(memcpy_test),
> -	KUNIT_CASE(memcpy_large_test),
>  	KUNIT_CASE(memmove_test),
> +	KUNIT_CASE(memcpy_large_test),
>  	KUNIT_CASE(memmove_large_test),
>  	KUNIT_CASE(memmove_overlap_test),
>  	KUNIT_CASE(strtomem_test),
> -- 
> 2.34.1
>