freezer: use lock_task_sighand() in fake_signal_wake_up()

cgroup_freezer calls freeze_task() without holding tasklist_lock and, if the task is exiting, its ->sighand may be gone by the time fake_signal_wake_up() is called. Use lock_task_sighand() instead of accessing ->sighand directly. Signed-off-by: Tejun Heo <[email protected]> Reported-by: Oleg Nesterov <[email protected]> Acked-by: Oleg Nesterov <[email protected]> Cc: "Rafael J. Wysocki" <[email protected]> Cc: Paul Menage <[email protected]>
niw · Nov 21, 2011 · 37ad8ac · 37ad8ac
1 parent 5ece3ea
commit 37ad8ac
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/kernel/freezer.c b/kernel/freezer.c
@@ -93,9 +93,10 @@ static void fake_signal_wake_up(struct task_struct *p)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&p->sighand->siglock, flags);
-	signal_wake_up(p, 0);
-	spin_unlock_irqrestore(&p->sighand->siglock, flags);
+	if (lock_task_sighand(p, &flags)) {
+		signal_wake_up(p, 0);
+		unlock_task_sighand(p, &flags);
+	}
 }
 
 /**