From: Will Deacon <will.deacon@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
Catalin Marinas <catalin.marinas@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Christoffer Dall <christoffer.dall@arm.com>,
Randy Dunlap <rdunlap@infradead.org>,
Dominik Brodowski <linux@dominikbrodowski.net>,
Julien Grall <julien.grall@arm.com>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v2 00/17] arm64 SSBD (aka Spectre-v4) mitigation
Date: Wed, 30 May 2018 16:58:55 +0100 [thread overview]
Message-ID: <20180530155854.GA4122@arm.com> (raw)
In-Reply-To: <20180529121121.24927-1-marc.zyngier@arm.com>
Hi Marc,
On Tue, May 29, 2018 at 01:11:04PM +0100, Marc Zyngier wrote:
> This patch series implements the Linux kernel side of the "Spectre-v4"
> (CVE-2018-3639) mitigation known as "Speculative Store Bypass Disable"
> (SSBD).
>
> More information can be found at:
>
> https://bugs.chromium.org/p/project-zero/issues/detail?id=1528
> https://developer.arm.com/support/arm-security-updates/speculative-processor-vulnerability
>
> For all released Arm Cortex-A CPUs that are affected by this issue, then
> the preferred mitigation is simply to set a chicken bit in the firmware
> during CPU initialisation and therefore no change to Linux is required.
> Other CPUs may require the chicken bit to be toggled dynamically (for
> example, when switching between user-mode and kernel-mode) and this is
> achieved by calling into EL3 via an SMC which has been published as part
> of the latest SMCCC specification:
>
> https://developer.arm.com/cache-speculation-vulnerability-firmware-specification
>
> as well as an ATF update for the released ARM cores affected by SSBD:
>
> https://github.com/ARM-software/arm-trusted-firmware/pull/1392
>
> These patches provide the following:
>
> 1. Safe probing of firmware to establish which CPUs in the system
> require calling into EL3 as part of the mitigation.
>
> 2. For CPUs that require it, call into EL3 on exception entry/exit
> from EL0 to apply the SSBD mitigation when running at EL1.
>
> 3. A command-line option to force the SSBD mitigation to be always on,
> always off, or dymamically toggled (default) for CPUs that require
> the EL3 call.
>
> 4. An initial implementation of a prctl() backend for arm64 that allows
> userspace tasks to opt-in to the mitigation explicitly. This is
> intended to match the interface provided by x86, and so we rely on
> their core changes here. The seccomp interface is provided as an
> extra set of patches, which I'd like *not* to see merged. The main
> reason is that it is invasive, has ugly/unclear semantics, and could
> probably be left to the existing prctl interface.
I agree with you here. For patches 1-10, then:
Acked-by: Will Deacon <will.deacon@arm.com>
but I'd prefer to leave the seccomp stuff alone for the moment because I
don't think the implicit enabling is necessarily the right thing to do
there and supporting it comes at a cost.
Will
next prev parent reply other threads:[~2018-05-30 15:58 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-29 12:11 [PATCH v2 00/17] arm64 SSBD (aka Spectre-v4) mitigation Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 01/17] arm/arm64: smccc: Add SMCCC-specific return codes Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 02/17] arm64: Call ARCH_WORKAROUND_2 on transitions between EL0 and EL1 Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 03/17] arm64: Add per-cpu infrastructure to call ARCH_WORKAROUND_2 Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 04/17] arm64: Add ARCH_WORKAROUND_2 probing Marc Zyngier
2018-05-29 13:39 ` Suzuki K Poulose
2018-05-29 12:11 ` [PATCH v2 05/17] arm64: Add 'ssbd' command-line option Marc Zyngier
2018-06-09 12:53 ` Jon Masters
2018-06-09 13:19 ` Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 06/17] arm64: ssbd: Add global mitigation state accessor Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 07/17] arm64: ssbd: Skip apply_ssbd if not using dynamic mitigation Marc Zyngier
2018-06-09 13:03 ` Jon Masters
2018-06-09 13:21 ` Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 08/17] arm64: ssbd: Restore mitigation status on CPU resume Marc Zyngier
2018-05-29 13:35 ` Mark Rutland
2018-05-29 12:11 ` [PATCH v2 09/17] arm64: ssbd: Introduce thread flag to control userspace mitigation Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 10/17] arm64: ssbd: Add prctl interface for per-thread mitigation Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 11/17] arm64: KVM: Add HYP per-cpu accessors Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 12/17] arm64: KVM: Add ARCH_WORKAROUND_2 support for guests Marc Zyngier
2018-06-09 13:09 ` Jon Masters
2018-06-09 13:21 ` Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 13/17] arm64: KVM: Handle guest's ARCH_WORKAROUND_2 requests Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 14/17] arm64: KVM: Add ARCH_WORKAROUND_2 discovery through ARCH_FEATURES_FUNC_ID Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 15/17] arm64: Add test_and_clear_flag and set_flag atomic assembler primitives Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 16/17] arm64: ssbd: Enable delayed setting of TIF_SSBD Marc Zyngier
2018-05-29 12:11 ` [PATCH v2 17/17] arm64: ssbd: Implement arch_seccomp_spec_mitigate Marc Zyngier
2018-05-30 15:58 ` Will Deacon [this message]
2018-05-31 16:41 ` [PATCH v2 00/17] arm64 SSBD (aka Spectre-v4) mitigation Catalin Marinas
2018-05-31 16:55 ` Marc Zyngier
2018-06-09 13:16 ` Jon Masters
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