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

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Date:   Mon, 9 Jan 2023 15:49:34 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>,
        linux-hardening@...r.kernel.org, David Gow <davidgow@...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 6, 2023 at 8:02 PM Kees Cook <keescook@...omium.org> 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>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
> Guenter, does this give you the needed flexibility to turn on the memcpy
> kunit tests again in your slower environments?
> ---
>  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
>


-- 
Thanks,
~Nick Desaulniers