linux-kernel - Re: [PATCH v2 3/4] KVM: arm64: Selftest for pKVM transitions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <867c5crd2j.wl-maz@kernel.org>
Date: Wed, 26 Feb 2025 14:32:52 +0000
From: Marc Zyngier <maz@...nel.org>
To: Quentin Perret <qperret@...gle.com>
Cc: Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] KVM: arm64: Selftest for pKVM transitions

On Tue, 25 Feb 2025 01:53:26 +0000,
Quentin Perret <qperret@...gle.com> wrote:
> 
> We have recently found a bug [1] in the pKVM memory ownership
> transitions by code inspection, but it could have been caught with a
> test.
> 
> Introduce a boot-time selftest exercising all the known pKVM memory
> transitions and importantly checks the rejection of illegal transitions.
> 
> The new test is hidden behind a new Kconfig option separate from
> CONFIG_EL2_NVHE_DEBUG on purpose as that has side effects on the
> transition checks ([1] doesn't reproduce with EL2 debug enabled).

That's a bit annoying, isn't it? Without EL2_DEBUG selected, you won't
get any stacktrace, and the WARN_ON()s are a guaranteed panic. Yes,
this is better than nothing, but I'm a bit worried this is going to be
hard to use.

Is there a way to reduce the impact the EL2 debug has on the rest of
the code? It feels like it is more invasive than it should be...

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.