[PATCH] x86: Improve handling of kernel mappings in change_page_attr

Fix various broken corner cases in i386 and x86-64 change_page_attr.

AK: split off from tighten kernel image access rights

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 12 insertions, 4 deletions

diff --git a/arch/x86_64/mm/pageattr.c b/arch/x86_64/mm/pageattr.c
index 76ee90a5abe0..bf4aa8dd4254 100644
--- a/arch/x86_64/mm/pageattr.c
+++ b/arch/x86_64/mm/pageattr.c
@@ -179,16 +179,24 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
 int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
 {
         unsigned long phys_base_pfn = __pa_symbol(__START_KERNEL_map) >> PAGE_SHIFT;
-        int err = 0; 
+        int err = 0, kernel_map = 0;
         int i; 
 
+        if (address >= __START_KERNEL_map
+            && address < __START_KERNEL_map + KERNEL_TEXT_SIZE) {
+                address = (unsigned long)__va(__pa(address));
+                kernel_map = 1;
+        }
+
         down_write(&init_mm.mmap_sem);
         for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
                 unsigned long pfn = __pa(address) >> PAGE_SHIFT;
 
-                err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
-                if (err) 
-                        break; 
+                if (!kernel_map || pte_present(pfn_pte(0, prot))) {
+                        err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
+                        if (err)
+                                break;
+                }
                 /* Handle kernel mapping too which aliases part of the
                  * lowmem */
                 if ((pfn >= phys_base_pfn) &&