linux-kernel - Re: [Patch] sunrpc: NULL utsname dereference on NFS umount during namespace cleanup

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Date:	Wed, 4 Feb 2015 22:52:30 +0100
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Trond Myklebust <trond.myklebust@...marydata.com>
Cc:	Nix <nix@...eri.org.uk>, "J. Bruce Fields" <bfields@...ldses.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: [Patch] sunrpc: NULL utsname dereference on NFS umount during
 namespace cleanup

On Wed, 4 Feb 2015 14:06:48 Trond Myklebust wrote:
> On Wed, Feb 4, 2015 at 12:08 PM, Bruno Prémont wrote:
> > On Fri, 30 January 2015 Trond Myklebust wrote:
> > > On Sun, 2015-01-25 at 16:55 -0500, Trond Myklebust wrote:
> > > > On Sun, Jan 25, 2015 at 4:06 PM, Bruno Prémont wrote:
> > > > > On a system running home-brown container (mntns, utsns,
> > > > > pidns, netns) with NFS mount-point bind-mounted into the
> > > > > container I hit the following trace if nfs filesystem is
> > > > > first umount()ed in init ns and then later umounted from
> > > > > container when the container exists.
> > > > >
> > > > > <snip trace>
> > > >
> > > > We should rather change rpcb_create() to pass the nodename from
> > > > the parent. The point is that the rpc_clnt->cl_nodename is used
> > > > in various different contexts (for instance in the AUTH_SYS
> > > > credential) where it isn't always appropriate to have it set to
> > > > an empty string.
> > >
> > > I was rather hoping that Bruno would fix up his patch and resend,
> > > but since other reports of the same bug are now surfacing...
> > > Please could you all check if something like the following patch
> > > fixes it.
> >
> > This patch works for me, so
> >   Tested-by: Bruno Prémont <bonbons@...ux-vserver.org>
> >
> > Now I get just the following complaint in dmesg on shutdown:
> >   [ 1940.173201] lockd: cannot unmonitor nfs.home
> >                                          ^^^^^^^^  name of NFS
> > server
> >
> > This complaint did not happen with my "empty string" name
> > patch.
> 
> Are there any clues from rpc.statd in your syslog that might help to
> explain the error?

I would say there is no more running rpc.statd at that time.

My shutdown process looks about as follows (it's not necessarily the
optimal ordering):

- umount nfs mountpoints from root mntns
- stop nfsclient
- stop rpc.statd
- stop rpcbind
- stop containers (with bind-mounted nfs mountpoints from root mntns
    that get implicitly umounted on mntns release)

Bruno
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