futex: pass nr_wake2 to futex_wake_op

The fourth argument of sys_futex is ignored when op == FUTEX_WAKE_OP,
but futex_wake_op expects it as its nr_wake2 parameter.

The only user of this operation in glibc is always passing 1, so this
bug had no consequences so far.
Signed-off-by: Andreas Schwab <schwab@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/futex.c

@@ -2060,8 +2060,10 @@ asmlinkage long sys_futex(u32 __user *uaddr, int op, u32 val,
 	}
 	/*
 	 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
+	 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
 	 */
-	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE)
+	if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
+	    cmd == FUTEX_WAKE_OP)
 		val2 = (u32) (unsigned long) utime;
 
 	return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);