linux-hardening - Re: [PATCH v1 0/8] Run KUnit tests late and handle faults

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Date: Fri, 1 Mar 2024 15:15:08 +0800
From: David Gow <davidgow@...gle.com>
To: Mickaël Salaün <mic@...ikod.net>
Cc: Brendan Higgins <brendanhiggins@...gle.com>, Kees Cook <keescook@...omium.org>, 
	Rae Moar <rmoar@...gle.com>, Shuah Khan <skhan@...uxfoundation.org>, 
	Alan Maguire <alan.maguire@...cle.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, "H . Peter Anvin" <hpa@...or.com>, 
	Ingo Molnar <mingo@...hat.com>, James Morris <jamorris@...ux.microsoft.com>, 
	Luis Chamberlain <mcgrof@...nel.org>, 
	"Madhavan T . Venkataraman" <madvenka@...ux.microsoft.com>, Marco Pagani <marpagan@...hat.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>, Stephen Boyd <sboyd@...nel.org>, 
	Thara Gopinath <tgopinath@...rosoft.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, 
	Zahra Tarkhani <ztarkhani@...rosoft.com>, kvm@...r.kernel.org, 
	linux-hardening@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, 
	linux-um@...ts.infradead.org, x86@...nel.org
Subject: Re: [PATCH v1 0/8] Run KUnit tests late and handle faults

On Fri, 1 Mar 2024 at 01:04, Mickaël Salaün <mic@...ikod.net> wrote:
>
> Hi,
>

Thanks very much. I think there's a lot going on in this series, and
it'd probably be easier to address if it were broken up a bit more.

To take things one at a time:

> This patch series moves KUnit test execution at the very end of kernel
> initialization, just before launching the init process.  This opens the
> way to test any kernel code in its normal state (i.e. fully
> initialized).

I like the general idea here, but there are a few things to keep in mind:
- We can already do this with tests built as modules.
- We have explicit support for testing __init code, so if we want to
keep that (and I think we do), we'll need to make sure that there
remains a way to run tests before __init.
- Behaviour changes here will need to be documented and tested well
across all tests and architectures, so it's not something I'd want to
land quickly.
- The requirement to have a root filesystem set up is another thing
we'll want to handle carefully.
- As-is, the patch seems to break arm64.

>
> This patch series also teaches KUnit to handle kthread faults as errors,
> and it brings a few related fixes and improvements.

These seem very good overall. I want to look at the last location
stuff in a bit more detail, but otherwise this is okay.

Personally, I'd like to see this split out into a separate series,
partly because I don't want to delay it while we sort the other parts
of this series out, and partly because I have some other changes to
the thread context stuff I think we need to make.

>
> New tests check NULL pointer dereference and read-only memory, which
> wasn't possible before.

These look interesting, but I don't like that they are listed as x86-specific.

>
> This is useful to test current kernel self-protection mechanisms or
> future ones such as Heki: https://github.com/heki-linux
>
> Regards,

Thanks again. I'll do a more detailed review of the individual patches
next week, but I'm excited to see this overall.

Cheers,
-- David


>
> Mickaël Salaün (8):
>   kunit: Run tests when the kernel is fully setup
>   kunit: Handle thread creation error
>   kunit: Fix kthread reference
>   kunit: Fix timeout message
>   kunit: Handle test faults
>   kunit: Fix KUNIT_SUCCESS() calls in iov_iter tests
>   kunit: Print last test location on fault
>   kunit: Add tests for faults
>
>  include/kunit/test.h                |  24 +++++-
>  include/kunit/try-catch.h           |   3 -
>  init/main.c                         |   4 +-
>  lib/bitfield_kunit.c                |   8 +-
>  lib/checksum_kunit.c                |   2 +-
>  lib/kunit/executor.c                |  81 ++++++++++++++------
>  lib/kunit/kunit-example-test.c      |   6 +-
>  lib/kunit/kunit-test.c              | 115 +++++++++++++++++++++++++++-
>  lib/kunit/try-catch.c               |  33 +++++---
>  lib/kunit_iov_iter.c                |  70 ++++++++---------
>  tools/testing/kunit/kunit_kernel.py |   6 +-
>  11 files changed, 261 insertions(+), 91 deletions(-)
>
>
> base-commit: d206a76d7d2726f3b096037f2079ce0bd3ba329b
> --
> 2.44.0
>

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