linux-kernel - Re: [RESEND PATCH] pid_ns: Fix proc_flush_task() accessing freed proc

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Message-ID: <20100625192945.GA25532@redhat.com>
Date:	Fri, 25 Jun 2010 21:29:45 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Containers <containers@...ts.osdl.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] pid_ns: Fix proc_flush_task() accessing freed
	proc_mnt

On 06/25, Sukadev Bhattiprolu wrote:
>
> Louis Rilling [Louis.Rilling@...labs.com] wrote:
> | - proc_pid_readdir():
> |   Needs similar check and protection to proc_pid_lookup(), but there is another
> |   issue: next_tgid() can find a dying task:
>
> Hmm, I thought proc_pid_readdir() would be a problem too but convinced myself
> that it would not - since a process running proc_pid_readdir() would have
> a reference to the pid namespace,

Where does this reference comes from ?

proc_pid_readdir() pins the task_struct (ns->child_reaper), not the pid/ns.

But I won't be surprised if I am wrong again ;)

Oleg.

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