1 files changed, 6 insertions, 3 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 13932abde159..8c6e1c17e6d3 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2735,21 +2735,24 @@ void cgroup_fork_callbacks(struct task_struct *child)
  * Called on every change to mm->owner. mm_init_owner() does not
  * invoke this routine, since it assigns the mm->owner the first time
  * and does not change it.
+ *
+ * The callbacks are invoked with mmap_sem held in read mode.
  */
 void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
 {
-        struct cgroup *oldcgrp, *newcgrp;
+        struct cgroup *oldcgrp, *newcgrp = NULL;
 
         if (need_mm_owner_callback) {
                 int i;
                 for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                         struct cgroup_subsys *ss = subsys[i];
                         oldcgrp = task_cgroup(old, ss->subsys_id);
-                        newcgrp = task_cgroup(new, ss->subsys_id);
+                        if (new)
+                                newcgrp = task_cgroup(new, ss->subsys_id);
                         if (oldcgrp == newcgrp)
                                 continue;
                         if (ss->mm_owner_changed)
-                                ss->mm_owner_changed(ss, oldcgrp, newcgrp);
+                                ss->mm_owner_changed(ss, oldcgrp, newcgrp, new);
                 }
         }
 }