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Subject: Re: [PATCH 4.4 00/37] 4.4.110-stable review
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Andy Lutomirski <luto@kernel.org>, Hugh Dickins <hughd@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Thomas Voegtle <tv@lio96.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Guenter Roeck <linux@roeck-us.net>,
        Shuah Khan <shuahkh@osg.samsung.com>, patches@kernelci.org,
        Ben Hutchings <ben.hutchings@codethink.co.uk>,
        lkft-triage@lists.linaro.org, stable <stable@vger.kernel.org>,
        Steve Sistare <steven.sistare@oracle.com>
References: <CAOAebxuqK4TOktLrHNLdW-S3oSxVO2og84js7N5u_QDC7mE2Ow@mail.gmail.com>
 <20180105204557.GA8839@kroah.com>
 <a93f30d1-e00e-419b-532d-203be16e2299@oracle.com>
 <20180107104540.GB14783@kroah.com>
 <CAOAebxsBVTyS2gSXh4c-g1b8Lvjv9MBG3Wjr_AC+LJpMLHRqEA@mail.gmail.com>
 <CAOAebxsP1LLV-Eg_h8brbxfsn_tpRDR46yrVZeokrFt3ArRuMA@mail.gmail.com>
 <20180108074645.GA24062@kroah.com>
 <CAOAebxu_gGE5chc-Mn=zBo_M3ojExvooNfvFRWOT=FygoffjLQ@mail.gmail.com>
 <CAOAebxuecMGOVe4zfNgk+t3mXVnDaWVA-GLdb+HiX3t9LNnxLg@mail.gmail.com>
 <CAOAebxu-OY-sxEZVzOkrG0iVG92ACiMNWk9xXVqZjj8kO5gp3A@mail.gmail.com>
 <20180111201006.GA29756@kroah.com>
From: Pavel Tatashin <pasha.tatashin@oracle.com>
Message-ID: <c01de3ab-5252-1f23-856a-660df7ec1016@oracle.com>
Date: Thu, 11 Jan 2018 15:18:43 -0500
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On 01/11/2018 03:10 PM, Greg Kroah-Hartman wrote:
> On Thu, Jan 11, 2018 at 01:36:50PM -0500, Pavel Tatashin wrote:
>> I have root caused the memory corruption panics/hangs that I've been
>> experiencing during boot with the latest 4.4.110 kernel. The problem
>> as was suspected by Andy Lutomirski is with interaction between PTI
>> and EFI. It may affect any system that has EFI bios.  I have not
>> verified if it can affect any other kernel beside 4.4.110
>>
>> Attached is the fix for this issue with explanations that Steve
>> Sistare and I developed.
> 
> Nice, but why does this not show up in 4.9 and 4.14 and Linus's tree as
> well on this hardware?  Nor on the SLES12 SP3 kernel?
> 
> What is different there that 4.4 requires?  That worries me more than
> your fix (which looks good to me, fwiw.)

Hi Greg,

I have not studied other versions of kernels, efi was changed 
substantially since 4.4. But, even on 4.4.110 there are several things 
have to happen for this bug to show-up:

1. During boot memmblock must allocate address that is not 2PAGE_SIZE 
aligned.
2. nmi must arrive exactly when EFI replaced page table.

While I was debugging this problem, I tried to enable, kasan, vm_debug, 
add more printfs etc, but every little change would cause this problem 
to disappear, or appear less frequently.

Thank you,
Pavel