Date: Mon, 30 Oct 2006 23:41:25 +0300
From: Oleg Nesterov <oleg@tv-sign.ru>
To: Jay Lan <jlan@engr.sgi.com>
Cc: Andrew Morton <akpm@osdl.org>, Shailabh Nagar <nagar@watson.ibm.com>,
       Balbir Singh <balbir@in.ibm.com>, Jay Lan <jlan@sgi.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [PATCH] xacct_add_tsk: fix pure theoretical ->mm use-after-free
Message-ID: <20061030204125.GB677@oleg>
References: <20061029185826.GA1619@oleg> <454649CE.80804@engr.sgi.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <454649CE.80804@engr.sgi.com>
User-Agent: Mutt/1.5.11
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 703
Lines: 22

On 10/30, Jay Lan wrote:
>
> Oleg Nesterov wrote:
> > Paranoid fix. The task can free its ->mm after the 'if (p->mm)' check.
> 
> Why this change is necessary? This routine is indirectly invoked by
> taskstats_exit_send() routine called inside do_exit():

Not only, please note

	taskstats_user_cmd(TASKSTATS_CMD_ATTR_PID)->fill_pid()->xacct_add_tsk()

path. This tsk is not 'current', it was found by find_task_by_pid(), and
it may exit at any time.

Oleg.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/