linux-kernel - Re: [PATCH v3 02/13] arm64: Kconfig: Reword UNMAP_KERNEL_AT

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Message-ID: <20180109171700.GA18100@infradead.org>
Date:   Tue, 9 Jan 2018 09:17:00 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Will Deacon <will.deacon@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
        ard.biesheuvel@...aro.org, marc.zyngier@....com,
        lorenzo.pieralisi@....com, christoffer.dall@...aro.org,
        linux-kernel@...r.kernel.org, shankerd@...eaurora.org,
        jnair@...iumnetworks.com
Subject: Re: [PATCH v3 02/13] arm64: Kconfig: Reword UNMAP_KERNEL_AT_EL0
 kconfig entry

On Mon, Jan 08, 2018 at 05:32:27PM +0000, Will Deacon wrote:
> Although CONFIG_UNMAP_KERNEL_AT_EL0 does make KASLR more robust, it's
> actually more useful as a mitigation against speculation attacks that
> can leak arbitrary kernel data to userspace through speculation.
> 
> Reword the Kconfig help message to reflect this, and make the option
> depend on EXPERT so that it is on by default for the majority of users.

I still haven't heard an anwer on why this isn't using
CONFIG_PAGE_TABLE_ISOLATION but instead reinvents its own symbol.