Re: [PATCH 2/2] NFS: NFSv4 readdir loses entries

[Bryan Schumaker <bjschuma@netapp.com>]

On 01/28/2011 12:41 PM, Chuck Lever wrote:
> 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@matisse cthon04]$
> 
> I narrowed the problem down to nfs4_decode_direct() reporting that the

I'm guessing that should be nfs4_decode_dirent()?

> 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".
> 
> Cc: stable@kernel.org [2.6.37]
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
> 
>  fs/nfs/nfs4xdr.c |    3 ---
>  1 files changed, 0 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index 009aef9..4e2c168 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -6132,9 +6132,6 @@ int nfs4_decode_dirent(struct xdr_stream *xdr, struct nfs_entry *entry,
>  	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 0;
>  
>  out_overflow:
> 
> --
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