1 files changed, 13 insertions, 0 deletions

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index e9fc1c1ae66c..c6c61ea6bb8c 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -591,16 +591,29 @@ static long do_set_mempolicy(unsigned short mode, unsigned short flags,
                              nodemask_t *nodes)
 {
         struct mempolicy *new;
+        struct mm_struct *mm = current->mm;
 
         new = mpol_new(mode, flags, nodes);
         if (IS_ERR(new))
                 return PTR_ERR(new);
+
+        /*
+         * prevent changing our mempolicy while show_numa_maps()
+         * is using it.
+         * Note:  do_set_mempolicy() can be called at init time
+         * with no 'mm'.
+         */
+        if (mm)
+                down_write(&mm->mmap_sem);
         mpol_put(current->mempolicy);
         current->mempolicy = new;
         mpol_set_task_struct_flag();
         if (new && new->policy == MPOL_INTERLEAVE &&
             nodes_weight(new->v.nodes))
                 current->il_next = first_node(new->v.nodes);
+        if (mm)
+                up_write(&mm->mmap_sem);
+
         return 0;
 }