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

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Message-ID: <20170920091555.GA3782@arm.com>
Date:   Wed, 20 Sep 2017 10:15:56 +0100
From:   Will Deacon <will.deacon@....com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Mark Salyzyn <salyzyn@...roid.com>,
        Catalin Marinas <catalin.marinas@....com>,
        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 Tue, Sep 19, 2017 at 03:02:22PM -0700, Kees Cook wrote:
> 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?

I haven't had chance to look at the patches yet (buried in other stuff), but
I aim to get to it in the next couple of weeks.

Will