linux-kernel - Re: [PATCH 2/3 V8] [tip:x86/mm] NX protection for kernel data

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Message-ID: <4C8FB616.2070807@free.fr>
Date:	Tue, 14 Sep 2010 19:51:18 +0200
From:	matthieu castet <castet.matthieu@...e.fr>
To:	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-next@...r.kernel.org
CC:	Arjan van de Ven <arjan@...radead.org>,
	James Morris <jmorris@...ei.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@....de>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Dave Jones <davej@...hat.com>,
	Siarhei Liakh <sliakh.lkml@...il.com>
Subject: Re: [PATCH 2/3 V8] [tip:x86/mm] NX protection for kernel data

Hi,

any feedback on that ?

Thanks,

Matthieu


matthieu castet a écrit :
>    Note: this patch depends on "Correct improper large page 
> preservation" patch
>       This patch expands functionality of CONFIG_DEBUG_RODATA to set main
>    (static) kernel data area as NX.
>    The following steps are taken to achieve this:
>    1. Linker script is adjusted so .text always starts and ends on a 
> page bound
>    2. Linker script is adjusted so .rodata always start and
>    end on a page boundary
>    3. NX is set for all pages from _etext through _end in mark_rodata_ro.
>    4. free_init_pages() sets released memory NX in arch/x86/mm/init.c
>    5. bios rom is set to x when pcibios is used.
>       The results of patch application may be observed in the diff of 
> kernel page
>    table dumps.
>    pcibios :
>    --- data_nx_pt_before.txt       2009-10-13 07:48:59.000000000 -0400
>    +++ data_nx_pt_after.txt        2009-10-13 07:26:46.000000000 -0400
>    @@ -2,8 +2,9 @@
>     0x00000000-0xc0000000           3G                           pmd
>     ---[ Kernel Mapping ]---
>    -0xc0000000-0xc0100000           1M     RW             GLB x  pte
>    +0xc0000000-0xc00a0000         640K     RW             GLB NX pte
>    +0xc00a0000-0xc0100000         384K     RW             GLB x  pte
>    -0xc0100000-0xc03d7000        2908K     ro             GLB x  pte
>    +0xc0100000-0xc0318000        2144K     ro             GLB x  pte
>    +0xc0318000-0xc03d7000         764K     ro             GLB NX pte
>    -0xc03d7000-0xc0600000        2212K     RW             GLB x  pte
>    +0xc03d7000-0xc0600000        2212K     RW             GLB NX pte
>     0xc0600000-0xf7a00000         884M     RW         PSE GLB NX pmd
>     0xf7a00000-0xf7bfe000        2040K     RW             GLB NX pte
>     0xf7bfe000-0xf7c00000           8K                           pte
>       no pcibios :
>    --- data_nx_pt_before.txt       2009-10-13 07:48:59.000000000 -0400
>    +++ data_nx_pt_after.txt        2009-10-13 07:26:46.000000000 -0400
>    @@ -2,8 +2,9 @@
>     0x00000000-0xc0000000           3G                           pmd
>     ---[ Kernel Mapping ]---
>    -0xc0000000-0xc0100000           1M     RW             GLB x  pte
>    +0xc0000000-0xc0100000           1M     RW             GLB NX pte
>    -0xc0100000-0xc03d7000        2908K     ro             GLB x  pte
>    +0xc0100000-0xc0318000        2144K     ro             GLB x  pte
>    +0xc0318000-0xc03d7000         764K     ro             GLB NX pte
>    -0xc03d7000-0xc0600000        2212K     RW             GLB x  pte
>    +0xc03d7000-0xc0600000        2212K     RW             GLB NX pte
>     0xc0600000-0xf7a00000         884M     RW         PSE GLB NX pmd
>     0xf7a00000-0xf7bfe000        2040K     RW             GLB NX pte
>     0xf7bfe000-0xf7c00000           8K                           pte
>       The patch have been developed for Linux 2.6.34-rc2 x86 by Siarhei 
> Liakh
>    <sliakh.lkml@...il.com> and Xuxian Jiang <jiang@...ncsu.edu>.
>       V1:  initial patch for 2.6.30
>    V2:  patch for 2.6.31-rc7
>    V3:  moved all code into arch/x86, adjusted credits
>    V4:  fixed ifdef, removed credits from CREDITS
>    V5:  fixed an address calculation bug in mark_nxdata_nx()
>    V6:  added acked-by and PT dump diff to commit log
>    V7:  minor adjustments for -tip
>    V8:  rework with the merge of "Set first MB as RW+NX"
>       Signed-off-by: Siarhei Liakh <sliakh.lkml@...il.com>
>    Signed-off-by: Xuxian Jiang <jiang@...ncsu.edu>
>    Signed-off-by: Matthieu CASTET <castet.matthieu@...e.fr>
> 

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