linux-kernel - Re: [PATCH 1/1] fix d_revalidate oopsen on NFS exports

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Message-ID: <20111201065024.GB495@boyd>
Date:	Thu, 1 Dec 2011 00:50:25 -0600
From:	Tyler Hicks <tyhicks@...onical.com>
To:	Chris Dunlop <chris@...he.net.au>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Eric Van Hensbergen <ericvh@...il.com>,
	Ron Minnich <rminnich@...dia.gov>,
	Latchesar Ionkov <lucho@...kov.net>,
	David Howells <dhowells@...hat.com>,
	Jan Harkes <jaharkes@...cmu.edu>,
	"maintainer:CODA FILE SYSTEM" <coda@...cmu.edu>,
	Dave Kleikamp <shaggy@...nel.org>,
	Petr Vandrovec <petr@...drovec.name>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	v9fs-developer@...ts.sourceforge.net,
	linux-afs@...ts.infradead.org, codalist@...EMANN.coda.cs.cmu.edu,
	jfs-discussion@...ts.sourceforge.net, linux-nfs@...r.kernel.org,
	ecryptfs@...r.kernel.org
Subject: Re: [PATCH 1/1] fix d_revalidate oopsen on NFS exports

On 2011-11-29 19:25:01, Chris Dunlop wrote:
> Hi,
> 
> I haven't seen any response to this patch which fixes an Oops in
> d_revalidate. I hit this using NFS, but various other file
> systems look to be likewise vulnerable, hence the broadness of
> the patch. The sequence leading to the Oops is:
> 
> lookup_one_len() [fs/namei.c]
>    calls __lookup_hash() [fs/namei.c] with nd == NULL,
>       which can then call the file system specific d_revalidate(), passing in nd == NULL
>          which will then Oops if nd is used without checking

Hey Chris - Can you share what you were trying to do when you hit this?
Were you stacking eCryptfs on top of NFS? Another stacked filesystem on
top of NFS?

Do you *need* a stacked filesystem to work on top of NFS? If so, we'll
need to discuss a way forward. Al has previously shown a dislike of
eCryptfs passing around nameidata (for good reason), but that is what
NFS currently requires. I looked at doing this a few months back, but
never got to the implementation stage.

As David mentioned, Al's atomic open patches might solve all of this in
the future, but I don't know much about that patchset. Is there any
relevant info you could provide about those patches, Al?

Tyler

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