linux-kernel - Re: rwx mapping between ex

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Message-ID: <6DF76AF6-E1A6-4C3B-9506-2B842F183B6F@zytor.com>
Date:	Mon, 28 Sep 2015 15:20:11 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Kees Cook <keescook@...omium.org>
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

Need to fix.  Not sure where the rwx mapping comes from.

On September 28, 2015 3:05:33 PM PDT, Kees Cook <keescook@...omium.org> wrote:
>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

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