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Message-ID: <817ecb6f0909031813n335279a3pb974b9efa8989095@mail.gmail.com>
Date: Thu, 3 Sep 2009 21:13:09 -0400
From: Siarhei Liakh <sliakh.lkml@...il.com>
To: linux-kernel@...r.kernel.org, linux-security-module@...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>, Rusty Russell <rusty@...tcorp.com.au>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>
Subject: [PATCH V3] x86: NX protection for kernel data
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 boundary
2. Linker script is adjusted so .rodata and .data always start and
end on a page boundary
3. void mark_nxdata_nx(void) added to arch/x86/mm/init.c with actual
functionality: NX is set for all pages from _etext through _end.
4. mark_nxdata_nx() called from free_initmem() (after init has been released)
5. free_init_pages() sets released memory NX in arch/x86/mm/init.c
The patch have been developed for Linux 2.6.31-rc7 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
---
Signed-off-by: Siarhei Liakh <sliakh.lkml@...il.com>
Signed-off-by: Xuxian Jiang <jiang@...ncsu.edu>
diff --git a/CREDITS b/CREDITS
index 1a41bf4..a24b669 100644
--- a/CREDITS
+++ b/CREDITS
@@ -1657,6 +1657,13 @@ N: Niels Kristian Bech Jensen
E: nkbj1970@...mail.com
D: Miscellaneous kernel updates and fixes.
+N: Xuxian Jiang
+E: jiang@...ncsu.edu
+D: RO/NX protection for static kernel and LKMs
+S: North Carolina State University
+S: Raleigh, North Carolina
+S: USA
+
N: Michael K. Johnson
E: johnsonm@...hat.com
W: http://www.redhat.com/~johnsonm
@@ -2068,6 +2075,13 @@ S: Post Office Box 371
S: North Little Rock, Arkansas 72115
S: USA
+N: Siarhei Liakh
+E: sliakh.lkml@...il.com
+D: RO/NX protection for static kernel and LKMs
+S: North Carolina State University
+S: Raleigh, North Carolina
+S: USA
+
N: Stephan Linz
E: linz@...et.de
E: Stephan.Linz@....de
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 78d185d..1b036e3 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -43,7 +43,7 @@ jiffies_64 = jiffies;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
- data PT_LOAD FLAGS(7); /* RWE */
+ data PT_LOAD FLAGS(6); /* RW_ */
#ifdef CONFIG_X86_64
user PT_LOAD FLAGS(7); /* RWE */
data.init PT_LOAD FLAGS(7); /* RWE */
@@ -89,6 +89,8 @@ SECTIONS
IRQENTRY_TEXT
*(.fixup)
*(.gnu.warning)
+ /* .text should occupy whole number of pages */
+ . = ALIGN(PAGE_SIZE);
/* End of text section */
_etext = .;
} :text = 0x9090
@@ -151,6 +153,8 @@ SECTIONS
.data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) {
*(.data.read_mostly)
+ /* .data should occupy whole number of pages */
+ . = ALIGN(PAGE_SIZE);
/* End of data section */
_edata = .;
}
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 0607119..9091bc0 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -423,9 +423,10 @@ void free_init_pages(char *what, unsigned long
begin, unsigned long end)
/*
* We just marked the kernel text read only above, now that
* we are going to free part of that, we need to make that
- * writeable first.
+ * writeable and non-executable first.
*/
set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);
+ set_memory_nx(begin, (end - begin) >> PAGE_SHIFT);
printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
@@ -440,11 +441,31 @@ void free_init_pages(char *what, unsigned long
begin, unsigned long end)
#endif
}
+#ifndef CONFIG_DEBUG_RODATA
+static inline void mark_nxdata_nx(void) { }
+#else
+void mark_nxdata_nx(void)
+{
+ /*
+ * When this called, init has already been executed and released,
+ * so everything past _etext sould be NX.
+ */
+ unsigned long start = PFN_ALIGN(_etext);
+ unsigned long size = PFN_ALIGN(_end) - start;
+
+ printk(KERN_INFO "NX-protecting the kernel data: %lx, %lu pages\n",
+ start, size >> PAGE_SHIFT);
+ set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);
+}
+#endif
+
void free_initmem(void)
{
free_init_pages("unused kernel memory",
(unsigned long)(&__init_begin),
(unsigned long)(&__init_end));
+ /* Set kernel's data as NX */
+ mark_nxdata_nx();
}
#ifdef CONFIG_BLK_DEV_INITRD
--
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