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Date: Wed, 13 May 2009 16:10:25 -0700
From: Greg KH <gregkh@suse.de>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kay Sievers <kay.sievers@vrfy.org>, Stephen Smalley <sds@tycho.nsa.gov>,
       David Howells <dhowells@redhat.com>,
       "David P. Quigley" <dpquigl@tycho.nsa.gov>, Greg KH <greg@kroah.com>,
       linux-kernel@vger.kernel.org, Jan Blunck <jblunck@suse.de>,
       James Morris <jmorris@namei.org>, Eric Paris <eparis@parisplace.org>,
       Christoph Hellwig <hch@infradead.org>
Subject: Re: [patch 00/13] devtmpfs patches
Message-ID: <20090513231025.GB12187@suse.de>
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On Wed, May 13, 2009 at 03:43:28PM -0700, Eric W. Biederman wrote:
> Kay Sievers <kay.sievers@vrfy.org> writes:
> 
> > On Wed, 2009-05-13 at 10:35 -0400, Stephen Smalley wrote:
> >> > Maybe we could do the same credential swap in sysfs, and get rid of:
> >> > /**
> >> >  * lookup_one_noperm - bad hack for sysfs
> >> > 
> >> > Seems a bit odd to have a vfs function for a single filesystem, called
> >> > from a single location, and annotated as "do not use". Christoph added
> >> > the comment a while ago, so adding him to Cc:.
> >> 
> >> Yes, that makes sense to me as well - we didn't have the credentials
> >> infrastructure in place at the time that lookup_one_noperm was
> >> introduced, but switching the credentials around a normal lookup_one_len
> >> call should work now.
> >
> > Something like this? It seems to work fine here, but I did not test it with SELinux.
> 
> That just masks the problem not fixes it.
> 
> The problem is that sysfs attempts to keep the dcache in lock-step with
> the sysfs_dentries.
> 
> The VFS model is lazy coherency and bringing things in sync on access.
> This is important to avoid locking problems.

So how would you propose to resolve this?

thanks,

greg k-h