linux-kernel - Re: [RFC] stack and heap are executable on x86

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Date:	Fri, 21 Dec 2012 13:26:36 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Jim Kukunas <james.t.kukunas@...ux.intel.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC] stack and heap are executable on x86_64

On Fri, Dec 21, 2012 at 9:36 AM, H. Peter Anvin <hpa@...or.com> wrote:
> We should NEVER have RW + x at the same time (at least when the kernel
> is compiled properly.)  Looks like your patch does get rid of a bunch of
> stuff in the low mapping -- although the low mapping really should never
> be +x at all -- but there are still problems with the high mapping

after enabling CONFIG_DEBUG_RODATA

get
---[ High Kernel Mapping ]---
0xffffffff80000000-0xffffffff81000000          16M                           pmd
0xffffffff81000000-0xffffffff82200000          18M     ro         PSE GLB x  pmd
0xffffffff82200000-0xffffffff82c00000          10M     ro         PSE GLB NX pmd
0xffffffff82c00000-0xffffffff82dc9000        1828K     RW             GLB x  pte
0xffffffff82dc9000-0xffffffff82e00000         220K     RW             GLB NX pte
0xffffffff82e00000-0xffffffff83000000           2M     RW         PSE GLB NX pmd
0xffffffff83000000-0xffffffff8313a000        1256K     RW             GLB NX pte
0xffffffff8313a000-0xffffffff83200000         792K     RW             GLB x  pte
0xffffffff83200000-0xffffffff83e00000          12M     RW         PSE GLB x  pmd
0xffffffff83e00000-0xffffffffa0000000         450M                           pmd

for
[    0.000000] Kernel Layout:
[    0.000000]   .text: [0x01000000-0x021434f8]
[    0.000000] .rodata: [0x02200000-0x02a13fff]
[    0.000000]   .data: [0x02c00000-0x02dc763f]
[    0.000000]   .init: [0x02dc9000-0x0312cfff]
[    0.000000]    .bss: [0x0313b000-0x03dd6fff]
[    0.000000]    .brk: [0x03dd7000-0x03dfffff]

looks like .data, .bss, .brk should not have x set.
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