linux-kernel - Re: [patch 00/13] devtmpfs patches

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Date:	Wed, 13 May 2009 16:10:25 -0700
From:	Greg KH <gregkh@...e.de>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Kay Sievers <kay.sievers@...y.org>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	David Howells <dhowells@...hat.com>,
	"David P. Quigley" <dpquigl@...ho.nsa.gov>,
	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Jan Blunck <jblunck@...e.de>, James Morris <jmorris@...ei.org>,
	Eric Paris <eparis@...isplace.org>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [patch 00/13] devtmpfs patches

On Wed, May 13, 2009 at 03:43:28PM -0700, Eric W. Biederman wrote:
> Kay Sievers <kay.sievers@...y.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
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