linux-kernel - Re: rwx mapping between ex

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Date:	Fri, 25 Sep 2015 09:25:33 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	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


* Kees Cook <keescook@...omium.org> wrote:

> On Thu, Sep 24, 2015 at 1:26 PM, Stephen Smalley <sds@...ho.nsa.gov> wrote:
> > Hi,
> >
> > With the attached config and 4.3-rc2 on x86_64, I see the following in /sys/kernel/debug/kernel_page_tables:
> > ...
> > ---[ High Kernel Mapping ]---
> > 0xffffffff80000000-0xffffffff81000000          16M                               pmd
> > 0xffffffff81000000-0xffffffff81600000           6M     ro         PSE     GLB x  pmd
> > 0xffffffff81600000-0xffffffff81775000        1492K     ro                 GLB x  pte
> > 0xffffffff81775000-0xffffffff81800000         556K     RW                 GLB x  pte
> > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Btw., I think we should run this lookup automatically in late bootup, if 
CONFIG_X86_PTDUMP=y, and print a WARN()ing if there's any RWX permissions in the 
mappings.

That makes sure automated testing picks new bugs up.

Thanks,

	Ingo
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