1 files changed, 20 insertions, 37 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 7a38ead96cae..45a13eb8894e 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -958,7 +958,8 @@ static inline void exit_pi_state_list(struct task_struct *curr) { }
  *	FUTEX_OWNER_DIED bit. See [4]
  *
  * [10] There is no transient state which leaves owner and user space
- *	TID out of sync.
+ *	TID out of sync. Except one error case where the kernel is denied
+ *	write access to the user address, see fixup_pi_state_owner().
  *
  *
  * Serialization and lifetime rules:
@@ -2480,6 +2481,24 @@ handle_err:
 	if (!err)
 		goto retry;
 
+	/*
+	 * fault_in_user_writeable() failed so user state is immutable. At
+	 * best we can make the kernel state consistent but user state will
+	 * be most likely hosed and any subsequent unlock operation will be
+	 * rejected due to PI futex rule [10].
+	 *
+	 * Ensure that the rtmutex owner is also the pi_state owner despite
+	 * the user space value claiming something different. There is no
+	 * point in unlocking the rtmutex if current is the owner as it
+	 * would need to wait until the next waiter has taken the rtmutex
+	 * to guarantee consistent state. Keep it simple. Userspace asked
+	 * for this wreckaged state.
+	 *
+	 * The rtmutex has an owner - either current or some other
+	 * task. See the EAGAIN loop above.
+	 */
+	pi_state_update_owner(pi_state, rt_mutex_owner(&pi_state->pi_mutex));
+
 	return err;
 }
 
@@ -2756,7 +2775,6 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
 			 ktime_t *time, int trylock)
 {
 	struct hrtimer_sleeper timeout, *to;
-	struct futex_pi_state *pi_state = NULL;
 	struct task_struct *exiting = NULL;
 	struct rt_mutex_waiter rt_waiter;
 	struct futex_hash_bucket *hb;
@@ -2892,23 +2910,8 @@ no_block:
 	if (res)
 		ret = (res < 0) ? res : 0;
 
-	/*
-	 * If fixup_owner() faulted and was unable to handle the fault, unlock
-	 * it and return the fault to userspace.
-	 */
-	if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current)) {
-		pi_state = q.pi_state;
-		get_pi_state(pi_state);
-	}
-
 	/* Unqueue and drop the lock */
 	unqueue_me_pi(&q);
-
-	if (pi_state) {
-		rt_mutex_futex_unlock(&pi_state->pi_mutex);
-		put_pi_state(pi_state);
-	}
-
 	goto out;
 
 out_unlock_put_key:
@@ -3168,7 +3171,6 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 				 u32 __user *uaddr2)
 {
 	struct hrtimer_sleeper timeout, *to;
-	struct futex_pi_state *pi_state = NULL;
 	struct rt_mutex_waiter rt_waiter;
 	struct futex_hash_bucket *hb;
 	union futex_key key2 = FUTEX_KEY_INIT;
@@ -3246,10 +3248,6 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		if (q.pi_state && (q.pi_state->owner != current)) {
 			spin_lock(q.lock_ptr);
 			ret = fixup_pi_state_owner(uaddr2, &q, current);
-			if (ret < 0 && rt_mutex_owner(&q.pi_state->pi_mutex) == current) {
-				pi_state = q.pi_state;
-				get_pi_state(pi_state);
-			}
 			/*
 			 * Drop the reference to the pi state which
 			 * the requeue_pi() code acquired for us.
@@ -3291,25 +3289,10 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		if (res)
 			ret = (res < 0) ? res : 0;
 
-		/*
-		 * If fixup_pi_state_owner() faulted and was unable to handle
-		 * the fault, unlock the rt_mutex and return the fault to
-		 * userspace.
-		 */
-		if (ret && rt_mutex_owner(&q.pi_state->pi_mutex) == current) {
-			pi_state = q.pi_state;
-			get_pi_state(pi_state);
-		}
-
 		/* Unqueue and drop the lock. */
 		unqueue_me_pi(&q);
 	}
 
-	if (pi_state) {
-		rt_mutex_futex_unlock(&pi_state->pi_mutex);
-		put_pi_state(pi_state);
-	}
-
 	if (ret == -EINTR) {
 		/*
 		 * We've already been requeued, but cannot restart by calling