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Message-ID: <4CE2F82E.60601@free.fr>
Date: Tue, 16 Nov 2010 22:31:26 +0100
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>,
Kees Cook <kees.cook@...onical.com>
Subject: [PATCH 2/3 V8] NX protection for kernel data
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>
View attachment "x86_nx_kernel_data.diff" of type "text/x-diff" (6786 bytes)
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