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Subject: Re: "bad pmd" errors + oops with KPTI on 4.14.11 after loading X.509 certs
From: Andy Lutomirski <luto@amacapital.net>
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In-Reply-To: <20180104003303.GA1654@trogon.sfo.coreos.systems>
Date: Wed, 3 Jan 2018 16:37:53 -0800
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, x86@kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        stable@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>
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To: Benjamin Gilbert <benjamin.gilbert@coreos.com>
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> On Jan 3, 2018, at 4:33 PM, Benjamin Gilbert <benjamin.gilbert@coreos.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