linux-kernel - Re: [RFC] Per-thread getrusage

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Date:	Mon, 28 Jan 2008 12:57:37 +0300
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Vinay Sridhar <vinay@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, libc-alpha@...rceware.org,
	drepper@...hat.com, wli@...omorphy.com, sripathik@...ibm.com,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [RFC] Per-thread getrusage

Andrew Morton wrote:
> On Mon, 28 Jan 2008 12:38:17 +0300 Pavel Emelyanov <xemul@...nvz.org> wrote:
> 
>>> If the code was using find_task_by_vpid() then OK (I guess).  But it is
>> Yup, find_task_by_vpid() will find the proper (i.e. in your namespace) task.
>>
>>> looking the tids up in the init_pid_ns.  Which I assume means that if it's
>>> in a new namespace and is looking up a sibling thread it will simply fail?
>> If it looks in the init_pid_ns, then it can either fail or obtain a task 
>> from different namespace. The find_task_by_pid_ns() was intended to be used
>> in proc mainly, to get tasks from the namespace pointed by the super-block
>> being explored.
>>
>> Please excuse my lamentable ignorance, but which code does such things with
>> init_pid_ns? I followed the 'per-thread rusage' thread and didn't find any.
> 
> From: Vinay Sridhar <vinay@...ux.vnet.ibm.com>
> To: linux-kernel@...r.kernel.org, libc-alpha@...rceware.org
> Cc: drepper@...hat.com, wli@...omorphy.com, akpm@...ux-foundation.org, sripathik@...ibm.com
> Subject: [RFC] Per-thread getrusage

Ouch. Thanks, I've missed that and looked just at the Roland's patch :(

> ...
> +asmlinkage long sys_thread_getrusage(int tid, struct rusage __user *ru)
> +{
> +	struct task_struct *tsk;
> +	tsk = find_task_by_pid(tid);
> +	return getrusage(tsk, RUSAGE_THREAD, ru);
> +}

Well, the find_task_by_pid() is really wrong here.

Besides (just in case this system call is going to be developed further), 
the tsk == NULL  case is not checked inside the getrusage and may OOPS 
even if the proper namespace is used.

Thanks,
Pavel

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