linux-kernel - Re: [PATCH 1/2] x86: consider effective protection attributes in W+X check

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Date:   Tue, 12 Dec 2017 03:43:56 -0700
From:   "Jan Beulich" <JBeulich@...e.com>
To:     "Ingo Molnar" <mingo@...nel.org>
Cc:     <mingo@...e.hu>, <tglx@...utronix.de>,
        "xen-devel" <xen-devel@...ts.xenproject.org>,
        "Boris Ostrovsky" <boris.ostrovsky@...cle.com>,
        "Juergen Gross" <jgross@...e.com>, <sds@...ho.nsa.gov>,
        <linux-kernel@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH 1/2] x86: consider effective protection attributes
 in W+X check

>>> On 12.12.17 at 11:36, <mingo@...nel.org> wrote:

> * Jan Beulich <JBeulich@...e.com> wrote:
> 
>> Using just the leaf page table entry flags would cause a false warning
>> in case _PAGE_RW is clear or _PAGE_NX is set in a higher level entry.
> 
> Good find - I assume this bug can cause both false positives and false 
> negatives 
> as well, right?

Yes, albeit I'm not aware of any outside of Xen (with that other patch
applied).

Jan