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From: Hugh Dickins <hughd@google.com>
Date: Wed, 3 Jan 2018 20:07:11 -0800
Message-ID: <CANsGZ6Yin_8JgRFBpBGxWCQCbrPnF92XuSghT9j_Dsk16KPAqg@mail.gmail.com>
Subject: Re: [PATCH 4.9 00/39] 4.9.75-stable review
To: Ben Hutchings <ben@decadent.org.uk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Shuah Khan <shuahkh@osg.samsung.com>, patches@kernelci.org,
        ben.hutchings@codethink.co.uk, lkft-triage@lists.linaro.org,
        stable <stable@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org

On Wed, Jan 3, 2018 at 5:24 PM, Ben Hutchings <ben@decadent.org.uk> wrote:
> On Wed, 2018-01-03 at 21:11 +0100, Greg Kroah-Hartman wrote:
>> This is the start of the stable review cycle for the 4.9.75 release.
>> There are 39 patches in this series, all will be posted as a response
>> to this one.  If anyone has any issues with these being applied, please
>> let me know.
> [...]
>
> This seems to be missing a backport of:
>
> commit 85900ea51577e31b186e523c8f4e068c79ecc7d3
> Author: Andy Lutomirski <luto@kernel.org>
> Date:   Tue Dec 12 07:56:42 2017 -0800
>
>     x86/pti: Map the vsyscall page if needed
>
> without which, KPTI will break some older user-space.

You're (kind of) right: I did warn Greg of that yesterday, and we were
both vaguely hoping that someone else could fill in that blank more
quickly than I'd get there.

I doubt it's an actual backport of Andy's 85900ea51577 that's needed -
I'd expect his to depend on at least some of the improved
infrastructure in 4.15-rc, rather than the old-style kaiser-mapping
employed in these backports.

Andrea has a RHEL7 patch for this, and I have a 3.2 patch derived from
Andrea's, but neither would be right for 4.9 or 4.4 as is: I think I'm
going to have to drop today's priority, and attend to this lacuna
tomorrow.

Hugh