Re: [PATCH] NFSD: do not return nfserr_symlink for the LINK operation

[Yang Hongyang <yanghy@cn.fujitsu.com>]

Hi,Bruce:
	what do you think of this patch,is this reasonable?

Yang Hongyang wrote:
> J. Bruce Fields wrote:
>> On Thu, Mar 19, 2009 at 05:46:45PM +0800, Yang Hongyang wrote:
>>> v1->v2:update some code style problem
>>> -------------------------
>>>
>>> There are four placees that returned inappropriate err nfserr_symlink accroding to 
>>> newpynfs test #LINK4a#LOOKP2a#OPCF3a#SATT12a.nfserr_symlink do not listed
>>> in these operations's err list in the spec.
>>> For LINK and LOOKUPP operation,nfserr_notdir should be returned.
>>> For OPEN_CONFIRM and SETATTR operation,nfserr_inval should be returned.
>> I thought Benny found that this also caused the linux client to return a
>> better error in one of these cases--could you confirm that and add a
>> mention of it in the commit message?
>>
>> (I'm reluctant to take patches like this based *only* on the spec
>> language, partly because rfc 3530 is known to have a few oversights in
>> the error listings.)
>>
>> I definitely appreciate people going through the pynfs tests and
>> investigating the results, but I don't want patch whose only
>> justification is that they quiet pynfs--we need to think about the
>> likely effect on real clients too.
>>
>> --b.
>>
> 
> Just as Bruce said:
> open_confirm is done with the same filehandle that was returned from a
> previous OPEN.  But an OPEN should never return the filehandle for a
> symlink.  That means for us to reach this case, either the client or our
> filesystem has a very serious bug.  Therefore, I'm not convinced that
> getting the error return correct in this case is worth the trouble.
> 
> OPEN_CONFIRM may never hit the error return.
> 
> And i did a test through following commands on a nfs4 fs:
> #touch test
> #ln -s test 1
> #ln 1 2
> 
> It just creat a symlink 2 to test as on the local fs.Accroding to
> this,I think link op will never hit the nfserr_symlink err return
> either.
> 
> For the reasons above,There seems to be only one op *LOOKUPP* that
> needs to be fixed.But still,I consider we should fix it all even the error
> return won't be triggered through real client use cauz there can be
> chances that a specially designed programme can triggered the bug.
> If the bug is not the return value issue but a memory overflow or some
> other strictness,the server may down by such attack.
> 
> -------------------------------------------------------------------------------------------
> There are four placees that returned inappropriate err nfserr_symlink accroding to 
> newpynfs test #LINK4a#LOOKP2a#OPCF3a#SATT12a.nfserr_symlink do not listed
> in these operations's err list in the spec.
> Benny Halevy pointed out  that the linux nfs client translates NFS4ERR_SYMLINK 
> to -ELOOP which is awkward and less descriptive to the app/user than
> -ENOTDIR. So a careful client implementation should never get NFS4ERR_SYMLINK
> if it stats the directory it operates on before sending the link op (or lookup, create,
>  rename, etc.) to make sure it is indeed a directory.
> [Sigh, looking at the code - it looks like we'll return NFS4ERR_ISDIR for a 
> length-changing SETATTR operating on a directory.  This is fine in NFSv4.0 
> but this error was removed for SETATTR in nfs4.1.  Note to self: revise
> this in the nfs41 tree]
> 
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> Reviewed-by: Benny Halevy <bhalevy@panasas.com>
> 
> ---
>  fs/nfsd/nfs4proc.c  |    6 +++++-
>  fs/nfsd/nfs4state.c |    6 +++++-
>  fs/nfsd/vfs.c       |    6 ++++++
>  3 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index 9fa60a3..9aaecaa 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -493,8 +493,12 @@ nfsd4_lookupp(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  		return nfserr_noent;
>  	}
>  	fh_put(&tmp_fh);
> -	return nfsd_lookup(rqstp, &cstate->current_fh,
> +	ret = nfsd_lookup(rqstp, &cstate->current_fh,
>  			   "..", 2, &cstate->current_fh);
> +	/* nfserr_symlink returned is inappropriate for LOOKUPP */
> +	if (ret == nfserr_symlink)
> +		ret = nfserr_notdir;
> +	return ret;
>  }
>  
>  static __be32
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index b6f60f4..28e4688 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2234,8 +2234,12 @@ nfsd4_open_confirm(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>  			cstate->current_fh.fh_dentry->d_name.name);
>  
>  	status = fh_verify(rqstp, &cstate->current_fh, S_IFREG, 0);
> -	if (status)
> +	if (status) {
> +		/* nfserr_symlink returned is inappropriate for OPEN_CONFIRM */
> +		if (status == nfserr_symlink)
> +			status = nfserr_inval;
>  		return status;
> +	}
>  
>  	nfs4_lock_state();
>  
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 6e50aaa..015a655 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -397,6 +397,9 @@ nfsd_setattr(struct svc_rqst *rqstp, struct svc_fh *fhp, struct iattr *iap,
>  		if (EX_ISSYNC(fhp->fh_export))
>  			write_inode_now(inode, 1);
>  out:
> +	/* nfserr_symlink returned is inappropriate for SETATTR */
> +	if (err == nfserr_symlink)
> +		err = nfserr_inval;
>  	return err;
>  
>  out_nfserr:
> @@ -1637,6 +1640,9 @@ out_dput:
>  out_unlock:
>  	fh_unlock(ffhp);
>  out:
> +	/* nfserr_symlink returned is inappropriate for LINK */
> +	if (err == nfserr_symlink)
> +		err = nfserr_notdir;
>  	return err;
>  
>  out_nfserr:


-- 
Regards
Yang Hongyang