1 files changed, 24 insertions, 9 deletions

diff --git a/kernel/futex.c b/kernel/futex.c
index b911adceb2c4..d73ef1f3e55d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -150,7 +150,8 @@ static struct futex_hash_bucket *hash_futex(union futex_key *key)
  */
 static inline int match_futex(union futex_key *key1, union futex_key *key2)
 {
-        return (key1->both.word == key2->both.word
+        return (key1 && key2
+                && key1->both.word == key2->both.word
                 && key1->both.ptr == key2->both.ptr
                 && key1->both.offset == key2->both.offset);
 }
@@ -303,8 +304,14 @@ void put_futex_key(int fshared, union futex_key *key)
  */
 static int fault_in_user_writeable(u32 __user *uaddr)
 {
-        int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
-                                 1, 1, 0, NULL, NULL);
+        struct mm_struct *mm = current->mm;
+        int ret;
+
+        down_read(&mm->mmap_sem);
+        ret = get_user_pages(current, mm, (unsigned long)uaddr,
+                             1, 1, 0, NULL, NULL);
+        up_read(&mm->mmap_sem);
+
         return ret < 0 ? ret : 0;
 }
 
@@ -916,8 +923,8 @@ retry:
         hb1 = hash_futex(&key1);
         hb2 = hash_futex(&key2);
 
-        double_lock_hb(hb1, hb2);
 retry_private:
+        double_lock_hb(hb1, hb2);
         op_ret = futex_atomic_op_inuser(op, uaddr2);
         if (unlikely(op_ret < 0)) {
 
@@ -1028,7 +1035,6 @@ static inline
 void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key,
                            struct futex_hash_bucket *hb)
 {
-        drop_futex_key_refs(&q->key);
         get_futex_key_refs(key);
         q->key = *key;
 
@@ -1226,6 +1232,7 @@ retry_private:
                  */
                 if (ret == 1) {
                         WARN_ON(pi_state);
+                        drop_count++;
                         task_count++;
                         ret = get_futex_value_locked(&curval2, uaddr2);
                         if (!ret)
@@ -1304,6 +1311,7 @@ retry_private:
                         if (ret == 1) {
                                 /* We got the lock. */
                                 requeue_pi_wake_futex(this, &key2, hb2);
+                                drop_count++;
                                 continue;
                         } else if (ret) {
                                 /* -EDEADLK */
@@ -1791,6 +1799,7 @@ static int futex_wait(u32 __user *uaddr, int fshared,
                                              current->timer_slack_ns);
         }
 
+retry:
         /* Prepare to wait on uaddr. */
         ret = futex_wait_setup(uaddr, val, fshared, &q, &hb);
         if (ret)
@@ -1808,9 +1817,14 @@ static int futex_wait(u32 __user *uaddr, int fshared,
                 goto out_put_key;
 
         /*
-         * We expect signal_pending(current), but another thread may
-         * have handled it for us already.
+         * We expect signal_pending(current), but we might be the
+         * victim of a spurious wakeup as well.
          */
+        if (!signal_pending(current)) {
+                put_futex_key(fshared, &q.key);
+                goto retry;
+        }
+
         ret = -ERESTARTSYS;
         if (!abs_time)
                 goto out_put_key;
@@ -2117,11 +2131,12 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
                  * Unqueue the futex_q and determine which it was.
                  */
                 plist_del(&q->list, &q->list.plist);
-                drop_futex_key_refs(&q->key);
 
+                /* Handle spurious wakeups gracefully */
+                ret = -EWOULDBLOCK;
                 if (timeout && !timeout->task)
                         ret = -ETIMEDOUT;
-                else
+                else if (signal_pending(current))
                         ret = -ERESTARTNOINTR;
         }
         return ret;