linux-kernel - Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

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Date:	Tue, 20 Oct 2009 03:27:00 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...l.org>, dlezcano@...ibm.com, jack@....cz,
	andrea@...share.com, sukadev@...ibm.com,
	Containers <containers@...ts.linux-foundation.org>,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>,
	mingo@...e.hu, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH] pidns: Fix a leak in /proc inodes and dentries

Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com> writes:

> Fix a leak in /proc dentries and inodes with pid namespaces.
>
> This fix reverts the commit 7766755a2f249e7e0. The leak was reported by
> Daniel Lezcano - see  http://lkml.org/lkml/2009/10/2/159.
>
> To summarize the thread, when container-init is terminated, it sets the
> PF_EXITING flag and then zaps all the other processes in the container.
> When those processes exit, they are expected to be reaped by the container-
> init and as a part of reaping, the container-init should flush any /proc
> dentries associated with the processes. But because the container-init is
> itself exiting and the following PF_EXITING check, the dentires are not
> flushed, resulting in leak in /proc inodes and dentries.

Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>

> Signed-off-by: Sukadev Bhattiprolu <sukadev@...ibm.com>
> Reported-by: Daniel Lezcano <dlezcano@...ibm.com>
> Cc: Eric W. Biederman <ebiederm@...ssion.com>
> Cc: Jan Kara <jack@....cz>
> Cc: Andrea Arcangeli <andrea@...share.com>
>
> ---
>  fs/proc/base.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> Index: linux-2.6/fs/proc/base.c
> ===================================================================
> --- linux-2.6.orig/fs/proc/base.c	2009-10-19 20:28:51.000000000 -0700
> +++ linux-2.6/fs/proc/base.c	2009-10-19 20:29:03.000000000 -0700
> @@ -2580,8 +2580,7 @@ static void proc_flush_task_mnt(struct v
>  	name.len = snprintf(buf, sizeof(buf), "%d", pid);
>  	dentry = d_hash_and_lookup(mnt->mnt_root, &name);
>  	if (dentry) {
> -		if (!(current->flags & PF_EXITING))
> -			shrink_dcache_parent(dentry);
> +		shrink_dcache_parent(dentry);
>  		d_drop(dentry);
>  		dput(dentry);
>  	}
--
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