Merge tag 'v4.1.40' into linux-linaro-lsk-v4.1lsk-v4.1-17.06lsk-v4.1-17.05linux-linaro-lsk-v4.1

 This is the 4.1.40 stable release

1 files changed, 10 insertions, 4 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index c67aab541ee2..4340fabad1b9 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -152,11 +152,17 @@ static void ptrace_unfreeze_traced(struct task_struct *task)
 
 	WARN_ON(!task->ptrace || task->parent != current);
 
+	/*
+	 * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely.
+	 * Recheck state under the lock to close this race.
+	 */
 	spin_lock_irq(&task->sighand->siglock);
-	if (__fatal_signal_pending(task))
-		wake_up_state(task, __TASK_TRACED);
-	else
-		task->state = TASK_TRACED;
+	if (task->state == __TASK_TRACED) {
+		if (__fatal_signal_pending(task))
+			wake_up_state(task, __TASK_TRACED);
+		else
+			task->state = TASK_TRACED;
+	}
 	spin_unlock_irq(&task->sighand->siglock);
 }