1 files changed, 39 insertions, 20 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index 3717e7b306e0..19eb089ca003 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -716,7 +716,7 @@ static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
                                 struct futex_pi_state **ps,
                                 struct task_struct *task, int set_waiters)
 {
-        int lock_taken, ret, ownerdied = 0;
+        int lock_taken, ret, force_take = 0;
         u32 uval, newval, curval, vpid = task_pid_vnr(task);
 
 retry:
@@ -755,17 +755,15 @@ retry:
         newval = curval | FUTEX_WAITERS;
 
         /*
-         * There are two cases, where a futex might have no owner (the
-         * owner TID is 0): OWNER_DIED. We take over the futex in this
-         * case. We also do an unconditional take over, when the owner
-         * of the futex died.
-         *
-         * This is safe as we are protected by the hash bucket lock !
+         * Should we force take the futex? See below.
          */
-        if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
-                /* Keep the OWNER_DIED bit */
+        if (unlikely(force_take)) {
+                /*
+                 * Keep the OWNER_DIED and the WAITERS bit and set the
+                 * new TID value.
+                 */
                 newval = (curval & ~FUTEX_TID_MASK) | vpid;
-                ownerdied = 0;
+                force_take = 0;
                 lock_taken = 1;
         }
 
@@ -775,7 +773,7 @@ retry:
                 goto retry;
 
         /*
-         * We took the lock due to owner died take over.
+         * We took the lock due to forced take over.
          */
         if (unlikely(lock_taken))
                 return 1;
@@ -790,20 +788,25 @@ retry:
                 switch (ret) {
                 case -ESRCH:
                         /*
-                         * No owner found for this futex. Check if the
-                         * OWNER_DIED bit is set to figure out whether
-                         * this is a robust futex or not.
+                         * We failed to find an owner for this
+                         * futex. So we have no pi_state to block
+                         * on. This can happen in two cases:
+                         *
+                         * 1) The owner died
+                         * 2) A stale FUTEX_WAITERS bit
+                         *
+                         * Re-read the futex value.
                          */
                         if (get_futex_value_locked(&curval, uaddr))
                                 return -EFAULT;
 
                         /*
-                         * We simply start over in case of a robust
-                         * futex. The code above will take the futex
-                         * and return happy.
+                         * If the owner died or we have a stale
+                         * WAITERS bit the owner TID in the user space
+                         * futex is 0.
                          */
-                        if (curval & FUTEX_OWNER_DIED) {
-                                ownerdied = 1;
+                        if (!(curval & FUTEX_TID_MASK)) {
+                                force_take = 1;
                                 goto retry;
                         }
                 default:
@@ -840,6 +843,9 @@ static void wake_futex(struct futex_q *q)
 {
         struct task_struct *p = q->task;
 
+        if (WARN(q->pi_state || q->rt_waiter, "refusing to wake PI futex\n"))
+                return;
+
         /*
          * We set q->lock_ptr = NULL _before_ we wake up the task. If
          * a non-futex wake up happens on another CPU then the task
@@ -1075,6 +1081,10 @@ retry_private:
 
         plist_for_each_entry_safe(this, next, head, list) {
                 if (match_futex (&this->key, &key1)) {
+                        if (this->pi_state || this->rt_waiter) {
+                                ret = -EINVAL;
+                                goto out_unlock;
+                        }
                         wake_futex(this);
                         if (++ret >= nr_wake)
                                 break;
@@ -1087,6 +1097,10 @@ retry_private:
                 op_ret = 0;
                 plist_for_each_entry_safe(this, next, head, list) {
                         if (match_futex (&this->key, &key2)) {
+                                if (this->pi_state || this->rt_waiter) {
+                                        ret = -EINVAL;
+                                        goto out_unlock;
+                                }
                                 wake_futex(this);
                                 if (++op_ret >= nr_wake2)
                                         break;
@@ -1095,6 +1109,7 @@ retry_private:
                 ret += op_ret;
         }
 
+out_unlock:
         double_unlock_hb(hb1, hb2);
 out_put_keys:
         put_futex_key(&key2);
@@ -1384,9 +1399,13 @@ retry_private:
                 /*
                  * FUTEX_WAIT_REQEUE_PI and FUTEX_CMP_REQUEUE_PI should always
                  * be paired with each other and no other futex ops.
+                 *
+                 * We should never be requeueing a futex_q with a pi_state,
+                 * which is awaiting a futex_unlock_pi().
                  */
                 if ((requeue_pi && !this->rt_waiter) ||
-                    (!requeue_pi && this->rt_waiter)) {
+                    (!requeue_pi && this->rt_waiter) ||
+                    this->pi_state) {
                         ret = -EINVAL;
                         break;
                 }