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

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Date:   Wed, 18 Jan 2023 12:43:43 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Guenter Roeck <linux@...ck-us.net>
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 12:32:16PM -0800, Guenter Roeck wrote:
> 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.

Ah-ha; thanks! I'll fix this in my tree.

-- 
Kees Cook