linux-kernel - Re: "bad pmd" errors + oops with KPTI on 4.14.11 after loading X.509 certs

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Date:   Wed, 3 Jan 2018 16:27:04 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Benjamin Gilbert <benjamin.gilbert@...eos.com>,
        Ingo Molnar <mingo@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        linux-mm@...ck.org, stable@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: "bad pmd" errors + oops with KPTI on 4.14.11 after loading X.509 certs



> On Jan 3, 2018, at 2:58 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> 
> 
>> On Wed, 3 Jan 2018, Thomas Gleixner wrote:
>> 
>>> On Wed, 3 Jan 2018, Benjamin Gilbert wrote:
>>>> On Wed, Jan 03, 2018 at 11:34:46PM +0100, Thomas Gleixner wrote:
>>>> Can you please send me your .config and a full dmesg ?
>>> 
>>> I've attached a serial log from a local QEMU.  I can rerun with a higher
>>> loglevel if need be.
>> 
>> Thanks!
>> 
>> Cc'ing Andy who might have an idea and he's probably more away than I
> 
> s/away/awake/ just to demonstrate the state I'm in ...
> 
>> am. Will have a look tomorrow if Andy does not beat me to it.

How much memory does the affected system have?  It sounds like something is mapped in the LDT region and is getting corrupted because the LDT code expects to own that region.

I got almost exactly this failure in an earlier version of the code when I typed the LDT base address macro.

I'll try to reproduce.

>> 
>> Thanks,
>> 
>>    tglx
>>