---

yaml
---
r: 75311
b: refs/heads/master
c: cdf71a1
h: refs/heads/master
i:
  75309: 7fa47a1
  75307: c1def75
  75303: 0c95a50
  75295: 52538ef
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: bf5e5834bffc62b50cd4a201804506eb11ef1af8
+refs/heads/master: cdf71a10c7b6432d9b48e292cca2c62a0b9fa6cf

trunk/kernel/futex.c

@@ -1097,15 +1097,15 @@ static void unqueue_me_pi(struct futex_q *q)
 }
 
 /*
- * Fixup the pi_state owner with current.
+ * Fixup the pi_state owner with the new owner.
  *
  * Must be called with hash bucket lock held and mm->sem held for non
  * private futexes.
  */
 static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
-				struct task_struct *curr)
+				struct task_struct *newowner)
 {
-	u32 newtid = task_pid_vnr(curr) | FUTEX_WAITERS;
+	u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
 	struct futex_pi_state *pi_state = q->pi_state;
 	u32 uval, curval, newval;
 	int ret;
@@ -1119,12 +1119,12 @@ static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
 	} else
 		newtid |= FUTEX_OWNER_DIED;
 
-	pi_state->owner = curr;
+	pi_state->owner = newowner;
 
-	spin_lock_irq(&curr->pi_lock);
+	spin_lock_irq(&newowner->pi_lock);
 	WARN_ON(!list_empty(&pi_state->list));
-	list_add(&pi_state->list, &curr->pi_state_list);
-	spin_unlock_irq(&curr->pi_lock);
+	list_add(&pi_state->list, &newowner->pi_state_list);
+	spin_unlock_irq(&newowner->pi_lock);
 
 	/*
 	 * We own it, so we have to replace the pending owner
@@ -1508,9 +1508,40 @@ static int futex_lock_pi(u32 __user *uaddr, struct rw_semaphore *fshared,
 		 * when we were on the way back before we locked the
 		 * hash bucket.
 		 */
-		if (q.pi_state->owner == curr &&
-		    rt_mutex_trylock(&q.pi_state->pi_mutex)) {
-			ret = 0;
+		if (q.pi_state->owner == curr) {
+			/*
+			 * Try to get the rt_mutex now. This might
+			 * fail as some other task acquired the
+			 * rt_mutex after we removed ourself from the
+			 * rt_mutex waiters list.
+			 */
+			if (rt_mutex_trylock(&q.pi_state->pi_mutex))
+				ret = 0;
+			else {
+				/*
+				 * pi_state is incorrect, some other
+				 * task did a lock steal and we
+				 * returned due to timeout or signal
+				 * without taking the rt_mutex. Too
+				 * late. We can access the
+				 * rt_mutex_owner without locking, as
+				 * the other task is now blocked on
+				 * the hash bucket lock. Fix the state
+				 * up.
+				 */
+				struct task_struct *owner;
+				int res;
+
+				owner = rt_mutex_owner(&q.pi_state->pi_mutex);
+				res = fixup_pi_state_owner(uaddr, &q, owner);
+
+				WARN_ON(rt_mutex_owner(&q.pi_state->pi_mutex) !=
+					owner);
+
+				/* propagate -EFAULT, if the fixup failed */
+				if (res)
+					ret = res;
+			}
 		} else {
 			/*
 			 * Paranoia check. If we did not take the lock