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Commit 5bd5a452 authored by Matthieu CASTET's avatar Matthieu CASTET Committed by Ingo Molnar
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x86: Add 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 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
  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
  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 has been originally developed for Linux 2.6.34-rc2 x86 by
Siarhei Liakh <sliakh.lkml@gmail.com> and Xuxian Jiang <jiang@cs.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: default avatarSiarhei Liakh <sliakh.lkml@gmail.com>
Signed-off-by: default avatarXuxian Jiang <jiang@cs.ncsu.edu>
Signed-off-by: default avatarMatthieu CASTET <castet.matthieu@free.fr>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: James Morris <jmorris@namei.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Dave Jones <davej@redhat.com>
Cc: Kees Cook <kees.cook@canonical.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <4CE2F82E.60601@free.fr>
[ minor cleanliness edits ]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 64edc8ed

arch/x86/include/asm/pci.h

+1 −0
Original line number Original line Diff line number Diff line
@@ -65,6 +65,7 @@ extern unsigned long pci_mem_start; 




#define PCIBIOS_MIN_CARDBUS_IO	0x4000

#define PCIBIOS_MIN_CARDBUS_IO	0x4000





extern int pcibios_enabled;

void pcibios_config_init(void);

void pcibios_config_init(void);

struct pci_bus *pcibios_scan_root(int bus);

struct pci_bus *pcibios_scan_root(int bus);

arch/x86/kernel/vmlinux.lds.S

+6 −2
Original line number Original line Diff line number Diff line
@@ -69,7 +69,7 @@ jiffies_64 = jiffies; 




PHDRS {

PHDRS {

	text PT_LOAD FLAGS(5);          /* R_E */

	text PT_LOAD FLAGS(5);          /* R_E */

	data PT_LOAD FLAGS(7);          /* RWE */

	data PT_LOAD FLAGS(6);          /* RW_ */

#ifdef CONFIG_X86_64

#ifdef CONFIG_X86_64

	user PT_LOAD FLAGS(5);          /* R_E */

	user PT_LOAD FLAGS(5);          /* R_E */

#ifdef CONFIG_SMP

#ifdef CONFIG_SMP
@@ -116,6 +116,10 @@ SECTIONS 




	EXCEPTION_TABLE(16) :text = 0x9090

	EXCEPTION_TABLE(16) :text = 0x9090





#if defined(CONFIG_DEBUG_RODATA)

	/* .text should occupy whole number of pages */

	. = ALIGN(PAGE_SIZE);

#endif

	X64_ALIGN_DEBUG_RODATA_BEGIN

	X64_ALIGN_DEBUG_RODATA_BEGIN

	RO_DATA(PAGE_SIZE)

	RO_DATA(PAGE_SIZE)

	X64_ALIGN_DEBUG_RODATA_END

	X64_ALIGN_DEBUG_RODATA_END
@@ -335,7 +339,7 @@ SECTIONS 
		__bss_start = .;

		__bss_start = .;

		*(.bss..page_aligned)

		*(.bss..page_aligned)

		*(.bss)

		*(.bss)

		. = ALIGN(4);

		. = ALIGN(PAGE_SIZE);

		__bss_stop = .;

		__bss_stop = .;

	}

	}

arch/x86/mm/init.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -364,8 +364,9 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end) 
	/*

	/*

	 * We just marked the kernel text read only above, now that

	 * We just marked the kernel text read only above, now that

	 * we are going to free part of that, we need to make that

	 * we are going to free part of that, we need to make that

	 * writeable first.

	 * writeable and non-executable first.

	 */

	 */

	set_memory_nx(begin, (end - begin) >> PAGE_SHIFT);

	set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);

	set_memory_rw(begin, (end - begin) >> PAGE_SHIFT);





	printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);

	printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);

arch/x86/mm/init_32.c

+19 −1
Original line number Original line Diff line number Diff line
@@ -226,7 +226,7 @@ page_table_range_init(unsigned long start, unsigned long end, pgd_t *pgd_base) 




static inline int is_kernel_text(unsigned long addr)

static inline int is_kernel_text(unsigned long addr)

{

{

	if (addr >= PAGE_OFFSET && addr <= (unsigned long)__init_end)

	if (addr >= (unsigned long)_text && addr <= (unsigned long)__init_end)

		return 1;

		return 1;

	return 0;

	return 0;

}

}
@@ -912,6 +912,23 @@ void set_kernel_text_ro(void) 
	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

}

}





static 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);

	/*

	 * This comes from is_kernel_text upper limit. Also HPAGE where used:

	 */

	unsigned long size = (((unsigned long)__init_end + HPAGE_SIZE) & HPAGE_MASK) - start;



	if (__supported_pte_mask & _PAGE_NX)

		printk(KERN_INFO "NX-protecting the kernel data: %luk\n", size >> 10);

	set_pages_nx(virt_to_page(start), size >> PAGE_SHIFT);

}



void mark_rodata_ro(void)

void mark_rodata_ro(void)

{

{

	unsigned long start = PFN_ALIGN(_text);

	unsigned long start = PFN_ALIGN(_text);
@@ -946,6 +963,7 @@ void mark_rodata_ro(void) 
	printk(KERN_INFO "Testing CPA: write protecting again\n");

	printk(KERN_INFO "Testing CPA: write protecting again\n");

	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

	set_pages_ro(virt_to_page(start), size >> PAGE_SHIFT);

#endif

#endif

	mark_nxdata_nx();

}

}

#endif

#endif

arch/x86/mm/init_64.c

+2 −1
Original line number Original line Diff line number Diff line
@@ -788,6 +788,7 @@ void mark_rodata_ro(void) 
	unsigned long rodata_start =

	unsigned long rodata_start =

		((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;

		((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK;

	unsigned long end = (unsigned long) &__end_rodata_hpage_align;

	unsigned long end = (unsigned long) &__end_rodata_hpage_align;

	unsigned long kernel_end = (((unsigned long)&__init_end + HPAGE_SIZE) & HPAGE_MASK);

	unsigned long text_end = PAGE_ALIGN((unsigned long) &__stop___ex_table);

	unsigned long text_end = PAGE_ALIGN((unsigned long) &__stop___ex_table);

	unsigned long rodata_end = PAGE_ALIGN((unsigned long) &__end_rodata);

	unsigned long rodata_end = PAGE_ALIGN((unsigned long) &__end_rodata);

	unsigned long data_start = (unsigned long) &_sdata;

	unsigned long data_start = (unsigned long) &_sdata;
@@ -802,7 +803,7 @@ void mark_rodata_ro(void) 
	 * The rodata section (but not the kernel text!) should also be

	 * The rodata section (but not the kernel text!) should also be

	 * not-executable.

	 * not-executable.

	 */

	 */

	set_memory_nx(rodata_start, (end - rodata_start) >> PAGE_SHIFT);

	set_memory_nx(rodata_start, (kernel_end - rodata_start) >> PAGE_SHIFT);





	rodata_test();

	rodata_test();