linux-kernel - Re: [PATCH v1 3/5] selftests/harness: Fix fixture teardown

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Date: Fri, 26 Apr 2024 12:40:32 -0700
From: Kees Cook <keescook@...omium.org>
To: Mickaël Salaün <mic@...ikod.net>
Cc: Christian Brauner <brauner@...nel.org>,
	Jakub Kicinski <kuba@...nel.org>, Mark Brown <broonie@...nel.org>,
	Shengyu Li <shengyu.li.evgeny@...il.com>,
	Shuah Khan <shuah@...nel.org>,
	"David S . Miller" <davem@...emloft.net>,
	Günther Noack <gnoack@...gle.com>,
	Will Drewry <wad@...omium.org>,
	kernel test robot <oliver.sang@...el.com>,
	linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
	Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v1 3/5] selftests/harness: Fix fixture teardown

On Fri, Apr 26, 2024 at 07:22:50PM +0200, Mickaël Salaün wrote:
> Make sure fixture teardowns are run when test cases failed, including
> when _metadata->teardown_parent is set to true.
> 
> Make sure only one fixture teardown is run per test case, handling the
> case where the test child forks.

I had to go look up __sync_bool_compare_and_swap(). :)

> 
> Cc: Shuah Khan <skhan@...uxfoundation.org>
> Cc: Shengyu Li <shengyu.li.evgeny@...il.com>
> Fixes: 72d7cb5c190b ("selftests/harness: Prevent infinite loop due to Assert in FIXTURE_TEARDOWN")
> Fixes: 0710a1a73fb4 ("selftests/harness: Merge TEST_F_FORK() into TEST_F()")
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> Link: https://lore.kernel.org/r/20240426172252.1862930-4-mic@digikod.net

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

-Kees

> ---
>  tools/testing/selftests/kselftest_harness.h | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/testing/selftests/kselftest_harness.h b/tools/testing/selftests/kselftest_harness.h
> index ba3ddeda24bf..73491efbae9e 100644
> --- a/tools/testing/selftests/kselftest_harness.h
> +++ b/tools/testing/selftests/kselftest_harness.h
> @@ -383,7 +383,10 @@
>  		FIXTURE_DATA(fixture_name) self; \
>  		pid_t child = 1; \
>  		int status = 0; \
> -		bool jmp = false; \
> +		/* Makes sure there is only one teardown, even when child forks again. */ \
> +		bool *teardown = mmap(NULL, sizeof(*teardown), \
> +			PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); \
> +		*teardown = false; \
>  		memset(&self, 0, sizeof(FIXTURE_DATA(fixture_name))); \
>  		if (setjmp(_metadata->env) == 0) { \
>  			/* Use the same _metadata. */ \
> @@ -400,15 +403,16 @@
>  				_metadata->exit_code = KSFT_FAIL; \
>  			} \
>  		} \
> -		else \
> -			jmp = true; \
>  		if (child == 0) { \
> -			if (_metadata->setup_completed && !_metadata->teardown_parent && !jmp) \
> +			if (_metadata->setup_completed && !_metadata->teardown_parent && \
> +					__sync_bool_compare_and_swap(teardown, false, true)) \
>  				fixture_name##_teardown(_metadata, &self, variant->data); \
>  			_exit(0); \
>  		} \
> -		if (_metadata->setup_completed && _metadata->teardown_parent) \
> +		if (_metadata->setup_completed && _metadata->teardown_parent && \
> +				__sync_bool_compare_and_swap(teardown, false, true)) \
>  			fixture_name##_teardown(_metadata, &self, variant->data); \
> +		munmap(teardown, sizeof(*teardown)); \
>  		if (!WIFEXITED(status) && WIFSIGNALED(status)) \
>  			/* Forward signal to __wait_for_test(). */ \
>  			kill(getpid(), WTERMSIG(status)); \
> -- 
> 2.44.0
> 

-- 
Kees Cook