Re: [Bug 201637] New: hangup sinse 'x86/mm: Expand static page table for fixmap space' with CONFIG_RANDOMIZE_BASE enabled

Re: [Bug 201637] New: hangup sinse 'x86/mm: Expand static page table for fixmap space' with CONFIG_RANDOMIZE_BASE enabled

[Andrew Morton]

(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@bugzilla.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@linux-foundation.org
>           Reporter: boyarsh@altlinux.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. 
> 
> commit 3a8304b7ad2e291777e8499e39390145d932a2fd
> Author: Feng Tang <feng.tang@intel.com>
> Date:   Thu Sep 20 10:58:28 2018 +0800
> 
>     x86/mm: Expand static page table for fixmap space
> 
>     commit 05ab1d8a4b36ee912b7087c6da127439ed0a903e upstream.
> 
>     We met a kernel panic when enabling earlycon, which is due to the fixmap
>     address of earlycon is not statically setup.
> 
> -- 
> You are receiving this mail because:
> You are the assignee for the bug.

Re: [Bug 201637] New: hangup sinse 'x86/mm: Expand static page table for fixmap space' with CONFIG_RANDOMIZE_BASE enabled

[Feng Tang]

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@bugzilla.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@linux-foundation.org
> >           Reporter: boyarsh@altlinux.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