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From: Andy Lutomirski <luto@kernel.org>
Date: Thu, 17 May 2018 14:07:03 -0700
Message-ID: <CALCETrWE3Y_GQfBtCjC4LbyWcAdt3bZKQTGdkjbS03ivoQ58hQ@mail.gmail.com>
Subject: Re: [4.11 Regression] 64-bit process gets AT_BASE in the first 4 GB
 if exec'ed from 32-bit process
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To: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Andrew Lutomirski <luto@kernel.org>, izbyshev@ispras.ru, Dmitry Safonov <dsafonov@virtuozzo.com>, Thomas Gleixner <tglx@linutronix.de>, Cyrill Gorcunov <gorcunov@openvz.org>, Borislav Petkov <bp@suse.de>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Alexander Monakov <amonakov@ispras.ru>, Linux-MM <linux-mm@kvack.org>

On Thu, May 17, 2018 at 1:51 PM Dmitry Safonov <0x7f454c46@gmail.com> wrote:

> 2018-05-17 21:46 GMT+01:00 Andy Lutomirski <luto@kernel.org>:
> > On Thu, May 17, 2018 at 1:25 PM Alexey Izbyshev <izbyshev@ispras.ru>
wrote:
> >
> >> Hello everyone,
> >
> >> I've discovered the following strange behavior of a 4.15.13-based
kernel
> >> (bisected to
> >
> >
> >
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1b028f784e8c341e762c264f70dc0ca1418c8b7a
> >> between 4.11-rc2 and -rc3 thanks to Alexander Monakov).
> >
> >
> > It's definitely not intended.  Can you confirm that the problem still
> > exists in 4.16?  I have some vague recollection that this was a known
issue
> > that got fixed, and we could plausibly just be missing a backport.

> I'm looking into that ATM, the problem like that was fixed with

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ada26481dfe6

> Will check what's happening there.

I haven't tried to figure out exactly what code calls which function, but
it seems like set_personality_64bit() really ought to clear TS_COMPAT.