[PATCH] x86_64: Fixed guard page handling again in iounmap

Caused oopses again.  Also fix potential mismatch in checking if
change_page_attr was needed.

To do it without races I needed to change mm/vmalloc.c to export a
__remove_vm_area that does not take vmlist lock.

Noticed by Terence Ripperda and based on a patch of his.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 20 insertions, 13 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 2bd83e5c2bbf..8ff16a1eee6a 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -248,31 +248,20 @@ struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
         return __get_vm_area(size, flags, VMALLOC_START, VMALLOC_END);
 }
 
-/**
- *      remove_vm_area  -  find and remove a contingous kernel virtual area
- *
- *      @addr:          base address
- *
- *      Search for the kernel VM area starting at @addr, and remove it.
- *      This function returns the found VM area, but using it is NOT safe
- *      on SMP machines.
- */
-struct vm_struct *remove_vm_area(void *addr)
+/* Caller must hold vmlist_lock */
+struct vm_struct *__remove_vm_area(void *addr)
 {
         struct vm_struct **p, *tmp;
 
-        write_lock(&vmlist_lock);
         for (p = &vmlist ; (tmp = *p) != NULL ;p = &tmp->next) {
                  if (tmp->addr == addr)
                          goto found;
         }
-        write_unlock(&vmlist_lock);
         return NULL;
 
 found:
         unmap_vm_area(tmp);
         *p = tmp->next;
-        write_unlock(&vmlist_lock);
 
         /*
          * Remove the guard page.
@@ -281,6 +270,24 @@ found:
         return tmp;
 }
 
+/**
+ *      remove_vm_area  -  find and remove a contingous kernel virtual area
+ *
+ *      @addr:          base address
+ *
+ *      Search for the kernel VM area starting at @addr, and remove it.
+ *      This function returns the found VM area, but using it is NOT safe
+ *      on SMP machines, except for its size or flags.
+ */
+struct vm_struct *remove_vm_area(void *addr)
+{
+        struct vm_struct *v;
+        write_lock(&vmlist_lock);
+        v = __remove_vm_area(addr);
+        write_unlock(&vmlist_lock);
+        return v;
+}
+
 void __vunmap(void *addr, int deallocate_pages)
 {
         struct vm_struct *area;