futex: additional (get|put)_futex_key() fixes

Impact: fix races

futex_requeue and futex_lock_pi still had some bad
(get|put)_futex_key() usage. This patch adds the missing
put_futex_keys() and corrects a goto in futex_lock_pi() to avoid
a double get.

Build and boot tested on a 4 way Intel x86_64 workstation.
Passes basic pthread_mutex and PI tests out of
ltp/testcases/realtime.
Signed-off-by: NDarren Hart <dvhltc@us.ibm.com>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <20090312075545.9856.75152.stgit@Aeon>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/futex.c

@@ -802,8 +802,10 @@ futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
 
 		ret = get_user(dummy, uaddr2);
 		if (ret)
-			return ret;
+			goto out_put_keys;
 
+		put_futex_key(fshared, &key2);
+		put_futex_key(fshared, &key1);
 		goto retryfull;
 	}
 
@@ -878,6 +880,9 @@ static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
 			if (hb1 != hb2)
 				spin_unlock(&hb2->lock);
 
+			put_futex_key(fshared, &key2);
+			put_futex_key(fshared, &key1);
+
 			ret = get_user(curval, uaddr1);
 
 			if (!ret)
@@ -1453,6 +1458,7 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
 			 * exit to complete.
 			 */
 			queue_unlock(&q, hb);
+			put_futex_key(fshared, &q.key);
 			cond_resched();
 			goto retry;
 
@@ -1595,13 +1601,12 @@ static int futex_lock_pi(u32 __user *uaddr, int fshared,
 
 	ret = get_user(uval, uaddr);
 	if (!ret)
-		goto retry;
+		goto retry_unlocked;
 
-	if (to)
-		destroy_hrtimer_on_stack(&to->timer);
-	return ret;
+	goto out_put_key;
 }
 
+
 /*
  * Userspace attempted a TID -> 0 atomic transition, and failed.
  * This is the in-kernel slowpath: we look up the PI state (if any),
@@ -1705,6 +1710,7 @@ static int futex_unlock_pi(u32 __user *uaddr, int fshared)
 	}
 
 	ret = get_user(uval, uaddr);
+	put_futex_key(fshared, &key);
 	if (!ret)
 		goto retry;