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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@xxxxxxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxxxxxxx
> >           Reporter: boyarsh@xxxxxxxxxxxx
> >         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