Date: Thu, 1 Dec 2011 00:50:25 -0600
From: Tyler Hicks <tyhicks@canonical.com>
To: Chris Dunlop <chris@onthe.net.au>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Eric Van Hensbergen <ericvh@gmail.com>,
        Ron Minnich <rminnich@sandia.gov>, Latchesar Ionkov <lucho@ionkov.net>,
        David Howells <dhowells@redhat.com>, Jan Harkes <jaharkes@cs.cmu.edu>,
        "maintainer:CODA FILE SYSTEM" <coda@cs.cmu.edu>,
        Dave Kleikamp <shaggy@kernel.org>,
        Petr Vandrovec <petr@vandrovec.name>,
        Trond Myklebust <Trond.Myklebust@netapp.com>,
        Greg Kroah-Hartman <gregkh@suse.de>, Al Viro <viro@zeniv.linux.org.uk>,
        v9fs-developer@lists.sourceforge.net, linux-afs@lists.infradead.org,
        codalist@TELEMANN.coda.cs.cmu.edu,
        jfs-discussion@lists.sourceforge.net, linux-nfs@vger.kernel.org,
        ecryptfs@vger.kernel.org
Subject: Re: [PATCH 1/1] fix d_revalidate oopsen on NFS exports
Message-ID: <20111201065024.GB495@boyd>
References: <1321861008-20611-1-git-send-email-chris@onthe.net.au>
 <20111129082501.GA569@onthe.net.au>
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On 2011-11-29 19:25:01, Chris Dunlop wrote:
> Hi,
>=20
> 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:
>=20
> lookup_one_len() [fs/namei.c]
>    calls __lookup_hash() [fs/namei.c] with nd =3D=3D NULL,
>       which can then call the file system specific d_revalidate(), passin=
g in nd =3D=3D 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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