linux-kernel - Re: [PATCH 3.16.y-ckt 009/170] NFS: Fix /proc/fs/nfsfs/servers and /proc/fs/nfsfs/volumes

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Date:	Fri, 14 Nov 2014 06:36:25 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Luis Henriques <luis.henriques@...onical.com>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com,
	Trond Myklebust <trond.myklebust@...marydata.com>,
	Stanislav Kinsbursky <skinsbursky@...allels.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 3.16.y-ckt 009/170] NFS: Fix /proc/fs/nfsfs/servers and
 /proc/fs/nfsfs/volumes

On Tue, 2014-11-11 at 11:06 +0000, Luis Henriques wrote:
> 3.16.7-ckt1 -stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: "Eric W. Biederman" <ebiederm@...ssion.com>
> 
> commit 65b38851a17472d31fec9019fc3a55b0802dab88 upstream.
> 
> The usage of pid_ns->child_reaper->nsproxy->net_ns in
> nfs_server_list_open and nfs_client_list_open is not safe.
> 
> /proc for a pid namespace can remain mounted after the all of the
> process in that pid namespace have exited.  There are also times
> before the initial process in a pid namespace has started or after the
> initial process in a pid namespace has exited where
> pid_ns->child_reaper can be NULL or stale.  Making the idiom
> pid_ns->child_reaper->nsproxy a double whammy of problems.
> 
> Luckily all that needs to happen is to move /proc/fs/nfsfs/servers and
> /proc/fs/nfsfs/volumes under /proc/net to /proc/net/nfsfs/servers and
> /proc/net/nfsfs/volumes and add a symlink from the original location,
> and to use seq_open_net as it has been designed.
> 
> Cc: Trond Myklebust <trond.myklebust@...marydata.com>
> Cc: Stanislav Kinsbursky <skinsbursky@...allels.com>
> Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
> Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
[...]

This needs a follow-up:

commit 21e81002f9788a3af591416b6dec60d7b67f2fb2
Author: Cong Wang <xiyou.wangcong@...il.com>
Date:   Mon Sep 8 16:17:55 2014 -0700

    nfs: fix kernel warning when removing proc entry

Ben.

-- 
Ben Hutchings
Never put off till tomorrow what you can avoid all together.

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