linux-kernel - [patch 17/29] NFS: NFSv4 readdir loses entries

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Date:	Thu, 10 Mar 2011 15:54:23 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Chuck Lever <chuck.lever@...cle.com>,
	Trond Myklebust <Trond.Myklebust@...app.com>
Subject: [patch 17/29] NFS: NFSv4 readdir loses entries

2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Chuck Lever <chuck.lever@...cle.com>

commit d1205f87bbb8040c1408bbd9e0a720310b2b0b9b upstream.

On recent 2.6.38-rc kernels, connectathon basic test 6 fails on
NFSv4 mounts of OpenSolaris with something like:

> ./test6: readdir
> 	./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.12' dir entry, pass 0
> 	./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.82' dir entry, pass 0
> 	./test6: (/mnt/klimt/matisse.test) didn't read expected 'file.164' dir entry, pass 0
> 	./test6: (/mnt/klimt/matisse.test) Test failed with 3 errors
> basic tests failed
> Tests failed, leaving /mnt/klimt mounted
> [cel@...isse cthon04]$

I narrowed the problem down to nfs4_decode_dirent() reporting that the
decode buffer had overflowed while decoding the entries for those
missing files.

verify_attr_len() assumes both it's pointer arguments reside on the
same page.  When these arguments point to locations on two different
pages, verify_attr_len() can report false errors.  This can happen now
that a large NFSv4 readdir result can span pages.

We have reasonably good checking in nfs4_decode_dirent() anyway, so
it should be safe to simply remove the extra checking.

At a guess, this was introduced by commit 6650239a, "NFS: Don't use
vm_map_ram() in readdir".

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@...app.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/nfs/nfs4xdr.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -6212,9 +6212,6 @@ __be32 *nfs4_decode_dirent(struct xdr_st
 	if (entry->fattr->valid & NFS_ATTR_FATTR_TYPE)
 		entry->d_type = nfs_umode_to_dtype(entry->fattr->mode);

-	if (verify_attr_len(xdr, p, len) < 0)
-		goto out_overflow;
-
 	return p;

 out_overflow:

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