linux-kernel - Re: [Bug 201637] New: hangup sinse 'x86/mm: Expand static page table for fixmap space' with CONFIG_RANDOMIZE

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Date:   Fri, 9 Nov 2018 09:29:29 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     bugzilla-daemon@...zilla.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Juergen Gross <jgross@...e.com>, Ingo Molnar <mingo@...e.hu>,
        "H. Peter Anvin" <hpa@...or.com>, boyarsh@...linux.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Bug 201637] New: hangup sinse  'x86/mm: Expand static page
 table for fixmap space' with CONFIG_RANDOMIZE_BASE enabled

Hi All,

On Thu, Nov 08, 2018 at 02:20:52PM -0800, Andrew Morton wrote:
> 
> (switched to email.  Please respond via emailed reply-to-all, not via the
> bugzilla web interface).
> 
> On Thu, 08 Nov 2018 13:48:25 +0000 bugzilla-daemon@...zilla.kernel.org wrote:
> 
> > https://bugzilla.kernel.org/show_bug.cgi?id=201637
> > 
> >             Bug ID: 201637
> >            Summary: hangup sinse  'x86/mm: Expand static page table for
> >                     fixmap space' with CONFIG_RANDOMIZE_BASE enabled
> >            Product: Memory Management
> >            Version: 2.5
> >     Kernel Version: 4.9.133
> >           Hardware: All
> >                 OS: Linux
> >               Tree: Mainline
> >             Status: NEW
> >           Severity: high
> >           Priority: P1
> >          Component: Other
> >           Assignee: akpm@...ux-foundation.org
> >           Reporter: boyarsh@...linux.org
> >         Regression: No
> > 
> > I have early kernel hungup on x86_64 since 4.9.133 and i've finaly bisected it.
> > 
> > This commit is incompatible with CONFIG_RANDOMIZE_BASE enabled and cause
> > immediate silent hangup during boot. 

Thanks for reporting. The patch revert was queued already. see
https://lkml.org/lkml/2018/11/2/453

And you are right, the problem is related with the kernel address randomization,
the original patch in mainline covers it, and the problem happens during my manual
backporting to 4.9, where I didn't fine head64.c and wrongly assumed KASLR was
not in 4.9 :(   sorry for the trouble. 

Thanks,
Feng