[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 6f38f818380b34edddfaae7a7494d926a33ff82d..f4ec722318358d2675dc57c1a58e55b0e3b72041 100644 (file)
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/arch/i386/kernel/vmlinux.lds.S
@@ -61,8 +61,6 @@ SECTIONS
        __stop___ex_table = .;
   }
 
-  RODATA
-
   BUG_TABLE
 
   . = ALIGN(4);
@@ -72,6 +70,8 @@ SECTIONS
        __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 23be1b0aafa4cd8b22043f2bd957b58ac88f0b8e..bd5ef37185044bb0526a96628010830888ab4c6e 100644 (file)
--- 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 @@ static int noinline do_test_wp_bit(void)
 
 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 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
                __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 36aa98a6d15cd3d1759b8d3d61d22028c7f8fa72..fd9fdfdd143ee1c00552c7fb0e326fc7b6a3c40c 100644 (file)
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -280,7 +280,6 @@ early_idt_ripmsg:
 
 .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 5176ecf006ee42fd71f46f49a781d0a98cc2e588..3bdeb88d28f4ffc2a8002ea588aa339973fbe4fa 100644 (file)
--- a/arch/x86_64/kernel/vmlinux.lds.S
+++ b/arch/x86_64/kernel/vmlinux.lds.S
@@ -29,6 +29,7 @@ SECTIONS
   .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 @@ SECTIONS
   __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 69e22d3c92382ea5f55f1a3cc660e389edc2c107..e3134bc9a4fc9ed302519159588b8f560cbb84c7 100644 (file)
--- 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 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
        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 free_initmem(void)
 
 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 3e628f990fdfd020d23d9e46163a8ea4f094ea78..89580b76495970387a1ead74a068762ac2178345 100644 (file)
--- 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