Avoid memory leak on fork() failure path.

Noticed by Martin Schwidefsky <schwidefsky@de.ibm.com>

kernel/fork.c

@@ -72,15 +72,8 @@ int nr_processes(void)
 	return total;
 }
 
-void __put_task_struct(struct task_struct *tsk)
+static void free_task_struct(struct task_struct *tsk)
 {
-	WARN_ON(!(tsk->state & (TASK_DEAD | TASK_ZOMBIE)));
-	WARN_ON(atomic_read(&tsk->usage));
-	WARN_ON(tsk == current);
-
-	security_task_free(tsk);
-	free_uid(tsk->user);
-
 	/*
 	 * The task cache is effectively disabled right now.
 	 * Do we want it? The slab cache already has per-cpu
@@ -103,6 +96,17 @@ void __put_task_struct(struct task_struct *tsk)
 	}
 }
 
+void __put_task_struct(struct task_struct *tsk)
+{
+	WARN_ON(!(tsk->state & (TASK_DEAD | TASK_ZOMBIE)));
+	WARN_ON(atomic_read(&tsk->usage));
+	WARN_ON(tsk == current);
+
+	security_task_free(tsk);
+	free_uid(tsk->user);
+	free_task_struct(tsk);
+}
+
 void add_wait_queue(wait_queue_head_t *q, wait_queue_t * wait)
 {
 	unsigned long flags;
@@ -1034,7 +1038,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	atomic_dec(&p->user->processes);
 	free_uid(p->user);
 bad_fork_free:
-	put_task_struct(p);
+	free_task_struct(p);
 	goto fork_out;
 }