linux-kernel - Re: [PATCH v2 9/9] selftests/harness: Fix vfork() side effects

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Date: Mon, 29 Apr 2024 08:57:58 -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
Subject: Re: [PATCH v2 9/9] selftests/harness: Fix vfork() side effects

On Mon, Apr 29, 2024 at 03:09:31PM +0200, Mickaël Salaün wrote:
> Setting the time namespace with CLONE_NEWTIME returns -EUSERS if the
> calling thread shares memory with another thread (because of the shared
> vDSO), which is the case when it is created with vfork().
> 
> Fix pidfd_setns_test by replacing test harness's vfork() call with a
> clone3() call with CLONE_VFORK, and an explicit sharing of the
> _metadata and self objects.
> 
> Replace _metadata->teardown_parent with a new FIXTURE_TEARDOWN_PARENT()
> helper that can replace FIXTURE_TEARDOWN().  This is a cleaner approach
> and it enables to selectively share the fixture data between the child
> process running tests and the parent process running the fixture
> teardown.  This also avoids updating several tests to not rely on the
> self object's copy-on-write property (e.g. storing the returned value of
> a fork() call).
> 
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: David S. Miller <davem@...emloft.net>
> Cc: Günther Noack <gnoack@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Mark Brown <broonie@...nel.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Will Drewry <wad@...omium.org>
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202403291015.1fcfa957-oliver.sang@intel.com
> Fixes: 0710a1a73fb4 ("selftests/harness: Merge TEST_F_FORK() into TEST_F()")
> Signed-off-by: Mickaël Salaün <mic@...ikod.net>

Thanks for splitting these up! I found it much more digestible. :)

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

-- 
Kees Cook