linux-kernel - Re: [PATCH 2/2] selftests/harness: Merge TEST_F_FORK() into TEST

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Date: Mon, 26 Feb 2024 11:04:12 -0800
From: Kees Cook <keescook@...omium.org>
To: Mickaël Salaün <mic@...ikod.net>
Cc: Jakub Kicinski <kuba@...nel.org>, Shuah Khan <shuah@...nel.org>,
	davem@...emloft.net,
	Günther Noack <gnoack@...gle.com>,
	Will Drewry <wad@...omium.org>, edumazet@...gle.com,
	jakub@...udflare.com, pabeni@...hat.com,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	linux-security-module@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] selftests/harness: Merge TEST_F_FORK() into TEST_F()

On Mon, Feb 26, 2024 at 05:23:35PM +0100, Mickaël Salaün wrote:
> Remplace Landlock-specific TEST_F_FORK() with an improved TEST_F() which
> brings four related changes:
> 
> Run TEST_F()'s tests in a grandchild process to make it possible to
> drop privileges and delegate teardown to the parent.
> 
> Compared to TEST_F_FORK(), simplify handling of the test grandchild
> process thanks to vfork(2), and makes it generic (e.g. no explicit
> conversion between exit code and _metadata).
> 
> Compared to TEST_F_FORK(), run teardown even when tests failed with an
> assert thanks to commit 63e6b2a42342 ("selftests/harness: Run TEARDOWN
> for ASSERT failures").
> 
> Simplify the test harness code by removing the no_print and step fields
> which are not used.  I added this feature just after I made
> kselftest_harness.h more broadly available but this step counter
> remained even though it wasn't needed after all. See commit 369130b63178
> ("selftests: Enhance kselftest_harness.h to print which assert failed").

I'm personally fine dropping the step counter. (I do wonder if that
removal should be split from the grandchild launching.)

> Replace spaces with tabs in one line of __TEST_F_IMPL().
> 
> Cc: Günther Noack <gnoack@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Will Drewry <wad@...omium.org>
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>

One typo below, but otherwise seems good to me:

Reviewed-by: Kees Cook <keescook@...omium.org>


> [...]
>  			_metadata->setup_completed = true; \
> -			fixture_name##_##test_name(_metadata, &self, variant->data); \
> +			/* Use the same _metadata. */ \
> +			child = vfork(); \
> +			if (child == 0) { \
> +				fixture_name##_##test_name(_metadata, &self, variant->data); \
> +				_exit(0); \
> +			} \
> +			if (child < 0) { \
> +				ksft_print_msg("ERROR SPAWNING TEST GANDCHILD\n"); \

typo: GAND -> GRAND

-- 
Kees Cook