[PATCH] x86: tighten kernel image page access rights
On x86-64, kernel memory freed after init can be entirely unmapped instead
of just getting 'poisoned' by overwriting with a debug pattern.
On i386 and x86-64 (under CONFIG_DEBUG_RODATA), kernel text and bug table
can also be write-protected.
Compared to the first version, this one prevents re-creating deleted
mappings in the kernel image range on x86-64, if those got removed
previously. This, together with the original changes, prevents temporarily
having inconsistent mappings when cacheability attributes are being
changed on such pages (e.g. from AGP code). While on i386 such duplicate
mappings don't exist, the same change is done there, too, both for
consistency and because checking pte_present() before using various other
pte_XXX functions is a requirement anyway. At once, i386 code gets
adjusted to use pte_huge() instead of open coding this.
AK: split out cpa() changes
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 6f38f81..f4ec722 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -61,8 +61,6 @@
__stop___ex_table = .;
}
- RODATA
-
BUG_TABLE
. = ALIGN(4);
@@ -72,6 +70,8 @@
__tracedata_end = .;
}
+ RODATA
+
/* writeable */
. = ALIGN(4096);
.data : AT(ADDR(.data) - LOAD_OFFSET) { /* Data */
diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index 23be1b0..bd5ef37 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -22,6 +22,7 @@
#include <linux/init.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
+#include <linux/pfn.h>
#include <linux/poison.h>
#include <linux/bootmem.h>
#include <linux/slab.h>
@@ -751,13 +752,25 @@
void mark_rodata_ro(void)
{
- unsigned long addr = (unsigned long)__start_rodata;
+ unsigned long start = PFN_ALIGN(_text);
+ unsigned long size = PFN_ALIGN(_etext) - start;
- for (; addr < (unsigned long)__end_rodata; addr += PAGE_SIZE)
- change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);
+#ifdef CONFIG_HOTPLUG_CPU
+ /* It must still be possible to apply SMP alternatives. */
+ if (num_possible_cpus() <= 1)
+#endif
+ {
+ change_page_attr(virt_to_page(start),
+ size >> PAGE_SHIFT, PAGE_KERNEL_RX);
+ printk("Write protecting the kernel text: %luk\n", size >> 10);
+ }
- printk("Write protecting the kernel read-only data: %uk\n",
- (__end_rodata - __start_rodata) >> 10);
+ start += size;
+ size = (unsigned long)__end_rodata - start;
+ change_page_attr(virt_to_page(start),
+ size >> PAGE_SHIFT, PAGE_KERNEL_RO);
+ printk("Write protecting the kernel read-only data: %luk\n",
+ size >> 10);
/*
* change_page_attr() requires a global_flush_tlb() call after it.
@@ -781,7 +794,7 @@
__free_page(page);
totalram_pages++;
}
- printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
+ printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
}
void free_initmem(void)
diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index 36aa98a..fd9fdfd 100644
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -280,7 +280,6 @@
.balign PAGE_SIZE
ENTRY(stext)
-ENTRY(_stext)
#define NEXT_PAGE(name) \
.balign PAGE_SIZE; \
diff --git a/arch/x86_64/kernel/vmlinux.lds.S b/arch/x86_64/kernel/vmlinux.lds.S
index 5176ecf..3bdeb88 100644
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/arch/x86_64/kernel/vmlinux.lds.S
@@ -29,6 +29,7 @@
.text : AT(ADDR(.text) - LOAD_OFFSET) {
/* First the code that has to be first for bootstrapping */
*(.bootstrap.text)
+ _stext = .;
/* Then all the functions that are "hot" in profiles, to group them
onto the same hugetlb entry */
#include "functionlist"
@@ -50,10 +51,10 @@
__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
__stop___ex_table = .;
- RODATA
-
BUG_TABLE
+ RODATA
+
. = ALIGN(PAGE_SIZE); /* Align data segment to page size boundary */
/* Data */
.data : AT(ADDR(.data) - LOAD_OFFSET) {
diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 69e22d3..e3134bc 100644
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -22,6 +22,7 @@
#include <linux/bootmem.h>
#include <linux/proc_fs.h>
#include <linux/pci.h>
+#include <linux/pfn.h>
#include <linux/poison.h>
#include <linux/dma-mapping.h>
#include <linux/module.h>
@@ -563,21 +564,23 @@
if (begin >= end)
return;
- printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
+ printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
for (addr = begin; addr < end; addr += PAGE_SIZE) {
struct page *page = pfn_to_page(addr >> PAGE_SHIFT);
ClearPageReserved(page);
init_page_count(page);
memset(page_address(page), POISON_FREE_INITMEM, PAGE_SIZE);
+ if (addr >= __START_KERNEL_map)
+ change_page_attr_addr(addr, 1, __pgprot(0));
__free_page(page);
totalram_pages++;
}
+ if (addr > __START_KERNEL_map)
+ global_flush_tlb();
}
void free_initmem(void)
{
- memset(__initdata_begin, POISON_FREE_INITDATA,
- __initdata_end - __initdata_begin);
free_init_pages("unused kernel memory",
__pa_symbol(&__init_begin),
__pa_symbol(&__init_end));
@@ -587,14 +590,18 @@
void mark_rodata_ro(void)
{
- unsigned long addr = (unsigned long)__va(__pa_symbol(&__start_rodata));
- unsigned long end = (unsigned long)__va(__pa_symbol(&__end_rodata));
+ unsigned long start = PFN_ALIGN(__va(__pa_symbol(&_stext))), size;
- for (; addr < end; addr += PAGE_SIZE)
- change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
+#ifdef CONFIG_HOTPLUG_CPU
+ /* It must still be possible to apply SMP alternatives. */
+ if (num_possible_cpus() > 1)
+ start = PFN_ALIGN(__va(__pa_symbol(&_etext)));
+#endif
+ size = (unsigned long)__va(__pa_symbol(&__end_rodata)) - start;
+ change_page_attr_addr(start, size >> PAGE_SHIFT, PAGE_KERNEL_RO);
- printk ("Write protecting the kernel read-only data: %luk\n",
- (__end_rodata - __start_rodata) >> 10);
+ printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
+ size >> 10);
/*
* change_page_attr_addr() requires a global_flush_tlb() call after it.
diff --git a/include/linux/poison.h b/include/linux/poison.h
index 3e628f9..89580b7 100644
--- a/include/linux/poison.h
+++ b/include/linux/poison.h
@@ -26,9 +26,6 @@
/********** arch/$ARCH/mm/init.c **********/
#define POISON_FREE_INITMEM 0xcc
-/********** arch/x86_64/mm/init.c **********/
-#define POISON_FREE_INITDATA 0xba
-
/********** arch/ia64/hp/common/sba_iommu.c **********/
/*
* arch/ia64/hp/common/sba_iommu.c uses a 16-byte poison string with a