linux-kernel - Re: rwx mapping between ex

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Message-ID: <CAGXu5jLBYxCjfn2c9h14OV=jHFK7y7cAzXkmZx98k-9ms8G=fQ@mail.gmail.com>
Date:	Mon, 28 Sep 2015 15:05:33 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	"x86@...nel.org" <x86@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: rwx mapping between ex_table and rodata

On Mon, Sep 28, 2015 at 2:16 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 09/25/2015 12:22 AM, Ingo Molnar wrote:
>>>
>>> To me it looks like another alignment/padding issue like got fixed
>>> before. The space between __ex_table and rodata is (seems?) unused, so
>>> the default page table permissions end up being W+X. Can we fix the
>>> default to be NX instead? It'll make these bugs stay gone.
>>
>> Yeah. Wanna send a patch for that?
>>
>
> At least in the high mapping space, the default should be no permissions
> (not present), rather than just NX.

Do you mean "should be" as in, that's how it's coded now, or "should
be" in that we need to fix it? (If we need to fix it, where is that
"default"? I haven't been able to find it yet.)

-Kees

-- 
Kees Cook
Chrome OS Security
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