[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>
This commit is contained in:
Jan Beulich
Andi Kleen
parent
d01ad8dd56
commit
6fb14755a6
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@ -61,8 +61,6 @@ SECTIONS
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__stop___ex_table = .;
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}
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RODATA
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BUG_TABLE
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. = ALIGN(4);
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@ -72,6 +70,8 @@ SECTIONS
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__tracedata_end = .;
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}
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RODATA
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/* writeable */
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. = ALIGN(4096);
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.data : AT(ADDR(.data) - LOAD_OFFSET) { /* Data */
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@ -22,6 +22,7 @@
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#include <linux/init.h>
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#include <linux/highmem.h>
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#include <linux/pagemap.h>
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#include <linux/pfn.h>
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#include <linux/poison.h>
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#include <linux/bootmem.h>
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#include <linux/slab.h>
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@ -751,13 +752,25 @@ static int noinline do_test_wp_bit(void)
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void mark_rodata_ro(void)
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{
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unsigned long addr = (unsigned long)__start_rodata;
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unsigned long start = PFN_ALIGN(_text);
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unsigned long size = PFN_ALIGN(_etext) - start;
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for (; addr < (unsigned long)__end_rodata; addr += PAGE_SIZE)
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change_page_attr(virt_to_page(addr), 1, PAGE_KERNEL_RO);
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#ifdef CONFIG_HOTPLUG_CPU
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/* It must still be possible to apply SMP alternatives. */
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if (num_possible_cpus() <= 1)
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#endif
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{
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change_page_attr(virt_to_page(start),
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size >> PAGE_SHIFT, PAGE_KERNEL_RX);
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printk("Write protecting the kernel text: %luk\n", size >> 10);
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}
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printk("Write protecting the kernel read-only data: %uk\n",
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(__end_rodata - __start_rodata) >> 10);
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start += size;
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size = (unsigned long)__end_rodata - start;
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change_page_attr(virt_to_page(start),
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size >> PAGE_SHIFT, PAGE_KERNEL_RO);
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printk("Write protecting the kernel read-only data: %luk\n",
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size >> 10);
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/*
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* change_page_attr() requires a global_flush_tlb() call after it.
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@ -781,7 +794,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
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__free_page(page);
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totalram_pages++;
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}
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printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
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printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
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}
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void free_initmem(void)
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@ -280,7 +280,6 @@ early_idt_ripmsg:
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.balign PAGE_SIZE
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ENTRY(stext)
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ENTRY(_stext)
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#define NEXT_PAGE(name) \
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.balign PAGE_SIZE; \
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@ -29,6 +29,7 @@ SECTIONS
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.text : AT(ADDR(.text) - LOAD_OFFSET) {
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/* First the code that has to be first for bootstrapping */
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*(.bootstrap.text)
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_stext = .;
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/* Then all the functions that are "hot" in profiles, to group them
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onto the same hugetlb entry */
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#include "functionlist"
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@ -50,10 +51,10 @@ SECTIONS
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__ex_table : AT(ADDR(__ex_table) - LOAD_OFFSET) { *(__ex_table) }
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__stop___ex_table = .;
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RODATA
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BUG_TABLE
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RODATA
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. = ALIGN(PAGE_SIZE); /* Align data segment to page size boundary */
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/* Data */
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.data : AT(ADDR(.data) - LOAD_OFFSET) {
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@ -22,6 +22,7 @@
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#include <linux/bootmem.h>
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#include <linux/proc_fs.h>
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#include <linux/pci.h>
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#include <linux/pfn.h>
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#include <linux/poison.h>
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#include <linux/dma-mapping.h>
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#include <linux/module.h>
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@ -563,21 +564,23 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
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if (begin >= end)
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return;
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printk(KERN_INFO "Freeing %s: %ldk freed\n", what, (end - begin) >> 10);
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printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
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for (addr = begin; addr < end; addr += PAGE_SIZE) {
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struct page *page = pfn_to_page(addr >> PAGE_SHIFT);
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ClearPageReserved(page);
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init_page_count(page);
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memset(page_address(page), POISON_FREE_INITMEM, PAGE_SIZE);
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if (addr >= __START_KERNEL_map)
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change_page_attr_addr(addr, 1, __pgprot(0));
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__free_page(page);
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totalram_pages++;
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}
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if (addr > __START_KERNEL_map)
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global_flush_tlb();
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}
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void free_initmem(void)
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{
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memset(__initdata_begin, POISON_FREE_INITDATA,
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__initdata_end - __initdata_begin);
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free_init_pages("unused kernel memory",
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__pa_symbol(&__init_begin),
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__pa_symbol(&__init_end));
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@ -587,14 +590,18 @@ void free_initmem(void)
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void mark_rodata_ro(void)
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{
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unsigned long addr = (unsigned long)__va(__pa_symbol(&__start_rodata));
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unsigned long end = (unsigned long)__va(__pa_symbol(&__end_rodata));
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unsigned long start = PFN_ALIGN(__va(__pa_symbol(&_stext))), size;
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for (; addr < end; addr += PAGE_SIZE)
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change_page_attr_addr(addr, 1, PAGE_KERNEL_RO);
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#ifdef CONFIG_HOTPLUG_CPU
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/* It must still be possible to apply SMP alternatives. */
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if (num_possible_cpus() > 1)
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start = PFN_ALIGN(__va(__pa_symbol(&_etext)));
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#endif
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size = (unsigned long)__va(__pa_symbol(&__end_rodata)) - start;
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change_page_attr_addr(start, size >> PAGE_SHIFT, PAGE_KERNEL_RO);
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printk ("Write protecting the kernel read-only data: %luk\n",
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(__end_rodata - __start_rodata) >> 10);
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printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n",
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size >> 10);
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/*
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* change_page_attr_addr() requires a global_flush_tlb() call after it.
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@ -26,9 +26,6 @@
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/********** arch/$ARCH/mm/init.c **********/
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#define POISON_FREE_INITMEM 0xcc
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/********** arch/x86_64/mm/init.c **********/
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#define POISON_FREE_INITDATA 0xba
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/********** arch/ia64/hp/common/sba_iommu.c **********/
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/*
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* arch/ia64/hp/common/sba_iommu.c uses a 16-byte poison string with a
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