Index: linux-2.6/mm/mempolicy.c
===================================================================
--- linux-2.6.orig/mm/mempolicy.c	2007-10-15 12:32:45.000000000 -0700
+++ linux-2.6/mm/mempolicy.c	2007-10-15 12:33:56.000000000 -0700
@@ -468,11 +468,13 @@ long do_set_mempolicy(int mode, nodemask
 	new = mpol_new(mode, nodes);
 	if (IS_ERR(new))
 		return PTR_ERR(new);
+	down_read(&current->mm->mmap_sem);
 	mpol_free(current->mempolicy);
 	current->mempolicy = new;
 	mpol_set_task_struct_flag();
 	if (new && new->policy == MPOL_INTERLEAVE)
 		current->il_next = first_node(new->v.nodes);
+	up_read(&current->mm->mmap_sem);
 	return 0;
 }