From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: akpm@linux-foundation.org, bigeasy@linutronix.de,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, marc.zyngier@arm.com,
peterx@redhat.com, rppt@kernel.org, walken@google.com,
yj.chiang@mediatek.com
Subject: Re: [PATCH] ARM: mm: harden branch predictor before opening interrupts during fault
Date: Tue, 26 Jan 2021 10:59:32 +0000 [thread overview]
Message-ID: <20210126105932.GG1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210126091708.3461-1-lecopzer.chen@mediatek.com>
On Tue, Jan 26, 2021 at 05:17:08PM +0800, Lecopzer Chen wrote:
> Hi all,
>
> I don't see any fix for this issue now(maybe I missed it..?),
> could we fix this if there is better solution?
> This issue exists almost two years.
I don't think anyone provided an acceptable patch.
The first patch moved the hardening out of the translation/section
fault handling. Since the kernel is mapped with sections, these
are above TASK_SIZE, and the whole point of the branch prediction
hardening is to prevent the prediction in the kernel being exploited,
missing the hardening effectively makes the mitigation useless.
The discussion in February 2019 never concluded from what I can see.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
WARNING: multiple messages have this Message-ID (diff)
From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Lecopzer Chen <lecopzer.chen@mediatek.com>
Cc: marc.zyngier@arm.com, bigeasy@linutronix.de,
linux-kernel@vger.kernel.org, peterx@redhat.com, rppt@kernel.org,
akpm@linux-foundation.org, walken@google.com,
yj.chiang@mediatek.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: mm: harden branch predictor before opening interrupts during fault
Date: Tue, 26 Jan 2021 10:59:32 +0000 [thread overview]
Message-ID: <20210126105932.GG1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20210126091708.3461-1-lecopzer.chen@mediatek.com>
On Tue, Jan 26, 2021 at 05:17:08PM +0800, Lecopzer Chen wrote:
> Hi all,
>
> I don't see any fix for this issue now(maybe I missed it..?),
> could we fix this if there is better solution?
> This issue exists almost two years.
I don't think anyone provided an acceptable patch.
The first patch moved the hardening out of the translation/section
fault handling. Since the kernel is mapped with sections, these
are above TASK_SIZE, and the whole point of the branch prediction
hardening is to prevent the prediction in the kernel being exploited,
missing the hardening effectively makes the mitigation useless.
The discussion in February 2019 never concluded from what I can see.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
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linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-01-26 11:42 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 9:27 [PATCH] ARM: mm: harden branch predictor before opening interrupts during fault Lecopzer Chen
2020-12-03 9:27 ` Lecopzer Chen
2021-01-26 9:17 ` Lecopzer Chen
2021-01-26 9:17 ` Lecopzer Chen
2021-01-26 10:59 ` Russell King - ARM Linux admin [this message]
2021-01-26 10:59 ` Russell King - ARM Linux admin
2021-01-26 11:07 ` Sebastian Andrzej Siewior
2021-01-26 11:07 ` Sebastian Andrzej Siewior
2021-01-26 15:01 ` Lecopzer Chen
2021-01-26 15:01 ` Lecopzer Chen
2021-01-26 15:29 ` Russell King - ARM Linux admin
2021-01-26 15:29 ` Russell King - ARM Linux admin
2021-01-26 16:03 ` Lecopzer Chen
2021-01-26 16:03 ` Lecopzer Chen
-- strict thread matches above, loose matches on Subject: below --
2019-03-19 20:32 Sebastian Andrzej Siewior
2019-04-15 11:08 ` Sebastian Andrzej Siewior
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