linux-hardening - Re: [PATCH v3] kunit: memcpy: Split slow memcpy tests into MEMCPY_SLOW_KUNIT

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Date:   Wed, 18 Jan 2023 12:32:16 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Kees Cook <keescook@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        David Gow <davidgow@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-hardening@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Alexander Potapenko <glider@...gle.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Isabella Basso <isabbasso@...eup.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] kunit: memcpy: Split slow memcpy tests into
 MEMCPY_SLOW_KUNIT_TEST

On Wed, Jan 18, 2023 at 12:06:54PM -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
> Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Reviewed-and-tested-by: Guenter Roeck <linux@...ck-us.net>
> Reviewed-by: David Gow <davidgow@...gle.com>
> 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>
> ---
> v3: fix defaults, avoid redundant returns.
> v2: https://lore.kernel.org/all/20230114005408.never.756-kees@kernel.org/
> v1: https://lore.kernel.org/lkml/20230107040203.never.112-kees@kernel.org
> ---
>  lib/Kconfig.debug  | 9 +++++++++
>  lib/memcpy_kunit.c | 3 +++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 881c3f84e88a..149d6403b8a9 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -2566,6 +2566,15 @@ config MEMCPY_KUNIT_TEST
>  
>  	  If unsure, say N.
>  
> +config MEMCPY_SLOW_KUNIT_TEST
> +	bool "Include exhaustive memcpy tests"
> +	depends on MEMCPY_KUNIT_TEST
> +	default y
> +	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, in case they need to be disabled.
> +
>  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..90f3aa9e909f 100644
> --- a/lib/memcpy_kunit.c
> +++ b/lib/memcpy_kunit.c
> @@ -309,6 +309,8 @@ static void set_random_nonzero(struct kunit *test, u8 *byte)
>  
>  static void 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");
>  
>  	/* Get many bit patterns. */
>  	get_random_bytes(large_src, ARRAY_SIZE(large_src));
> @@ -327,6 +329,7 @@ static void init_large(struct kunit *test)
>   */
>  static void copy_large_test(struct kunit *test, bool use_memmove)
>  {
> +

Some whitespace noise slipped in here.

Guenter

>  	init_large(test);
>  
>  	/* Copy a growing number of non-overlapping bytes ... */
> -- 
> 2.34.1
>