linux-kernel - Re: [PATCH v3 0/3] arm64: Add CONFIG_KUSER

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Date:   Tue, 19 Sep 2017 15:02:22 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Mark Salyzyn <salyzyn@...roid.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kevin.brodsky@....com,
        Ingo Molnar <mingo@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        James Morse <james.morse@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Martin <Dave.Martin@....com>, credmonster@...il.com,
        zijun_hu <zijun_hu@....com>, Mark Rutland <mark.rutland@....com>,
        Jisheng Zhang <jszhang@...vell.com>,
        Laura Abbott <labbott@...hat.com>,
        John Stultz <john.stultz@...aro.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Michal Marek <mmarek@...e.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH v3 0/3] arm64: Add CONFIG_KUSER_HELPERS

On Mon, Sep 11, 2017 at 8:26 AM, Mark Salyzyn <salyzyn@...roid.com> wrote:
> Make it possible to disable the kuser helpers by adding a KUSER_HELPERS
> config option (enabled by default). When disabled, all kuser
> helpers-related code is removed from the kernel and no mapping is done
> at the fixed high address (0xffff0000); any attempt to use a kuser
> helper from a 32-bit process will result in a segfault.
>
> Signed-off-by: Mark Salyzyn <salyzyn@...roid.com>
>
> v2:
> - vectors_page and compat_vdso_spec as array of 2
> - free sigpage if vectors allocation failed
> - adjust makefile so one line for each of the assembler source modules
> - split off assembler changes to a new previous patch in series to reduce churn
> - modify slightly the feature documentation to reduce its reach
> - modify slightly the feature documentation to rationalize the yes default.
> - There are more ifdefs as a result of the rebase.
>
> v3:
> - rebase (minor conflicts)

This looks great to me. I'd love to see kuser helpers gone. :)

Catalin, Will, does this need anything else?

-Kees

-- 
Kees Cook
Pixel Security