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 16:37:53 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Benjamin Gilbert <benjamin.gilbert@...eos.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.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 4:33 PM, Benjamin Gilbert <benjamin.gilbert@...eos.com> wrote:
> 
>> On Wed, Jan 03, 2018 at 10:20:16AM +0100, Greg Kroah-Hartman wrote:
>> Ick, not good, any chance you can test 4.15-rc6 to verify that the issue
>> is also there (or not)?
> 
> I haven't been able to reproduce this on 4.15-rc6.

Ah.  Maybe try rebuilding a bad kernel with free_ldt_pgtables() modified to do nothing, and the read /sys/kernel/debug/page_tables/current (or current_kernel, or whatever it's called).  The problem may be obvious.

> 
> --Benjamin Gilbert