linux-kernel - Re: [BUG] madvise05 leads kernel panic on 4.9.122

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Date:   Tue, 21 Aug 2018 13:36:31 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     yang.shi@...ux.alibaba.com
Cc:     David Woodhouse <dwmw2@...radead.org>, gregkh@...uxfoundation.org,
        tglx@...utronix.de, dave.hansen@...el.com, stable@...r.kernel.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUG] madvise05 leads kernel panic on 4.9.122

On Tue, Aug 21, 2018 at 01:30:20PM -0700, yang.shi@...ux.alibaba.com wrote:
> 
> 
> On 8/21/18 11:43 AM, David Woodhouse wrote:
> > On Tue, 2018-08-21 at 11:37 -0700, Yang Shi wrote:
> > > I just ran some regression test on stable 4.9.122 with LTP. madvise05
> > > triggers the below kernel panic:
> 
> Thanks, David. It works. A silly question, I don't get why this commit could
> solve this issue, it looks just like a code refactor. Just because it
> changed how to get pfn from page table entries? And, this may cause some
> mismatch on 4.9 stable without it?

With the L1TF patches open coded pte_val() to get the PFN can cause problems
because it doesn't do the invert for PROT_NONE mappings

The cleanup changes the open coded versions to use p*_pfn(), which always
works correctly.

-Andi