Re: hit a KASan bug related to Perf during stress test

[Peter Zijlstra <peterz@infradead.org>]

On Mon, Oct 24, 2016 at 02:02:32PM +0200, Oleg Nesterov wrote:
> Perhaps. Or into task_tgid(). Or even the patch below, __task_pid_nr_ns()
> is always safe. This certainly needs some cleanups.


> --- x/include/linux/pid.h
> +++ x/include/linux/pid.h
> @@ -8,7 +8,8 @@ enum pid_type
>  	PIDTYPE_PID,
>  	PIDTYPE_PGID,
>  	PIDTYPE_SID,
> -	PIDTYPE_MAX
> +	PIDTYPE_MAX,
> +	PIDTYPE_TGID	/* do not use */
>  };
>  
>  /*
> --- x/kernel/pid.c
> +++ x/kernel/pid.c
> @@ -538,7 +538,7 @@ EXPORT_SYMBOL(__task_pid_nr_ns);
>  
>  pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
>  {
> -	return pid_nr_ns(task_tgid(tsk), ns);
> +	return __task_pid_nr_ns(tsk, PIDTYPE_TGID, ns);
>  }
>  EXPORT_SYMBOL(task_tgid_nr_ns);
>  
> 

Right, that will return 0 on !alive. But I'm not seeing how PIDTYPE_TGID
isn't an array bound violating of its own though. Then again, I didn't
look to hard at the pid stuff.