Re: [PATCH 2/2 v2] nfsd41: check the size of request

From: Mi Jinlong <mijinlong@cn.fujitsu.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: NFS <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH 2/2 v2] nfsd41: check the size of request
Date: Fri, 08 Jul 2011 17:13:44 +0800	[thread overview]
Message-ID: <4E16CA48.3030308@cn.fujitsu.com> (raw)
In-Reply-To: <20110706164306.GC30349@fieldses.org>

J. Bruce Fields 写道:
> On Sat, Jul 02, 2011 at 05:02:54PM +0800, Mi Jinlong wrote:
>> This patch just check request's size when it consists SEQUENCE.
>>
>> Signed-off-by: Mi Jinlong <mijinlong@cn.fujitsu.com>
>> ---
>>  fs/nfsd/nfs4state.c |   16 ++++++++++++++++
>>  1 files changed, 16 insertions(+), 0 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index e98f3c2..17e30bf 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -1736,6 +1736,21 @@ static bool nfsd4_session_too_many_ops(struct svc_rqst *rqstp, struct nfsd4_sess
>>  	return args->opcnt > session->se_fchannel.maxops;
>>  }
>>  
>> +static int nfsd4_check_request_size(struct nfsd4_compoundargs *args,
>> +				    struct nfsd4_session *session)
>> +{
>> +	struct xdr_buf *xb = &args->rqstp->rq_arg;
>> +
>> +	/* Only SEQUENCE operation */
>> +	if (args->opcnt == 1)
>> +		return 0;
> 
> Do we need this special check?
> 
> Sure, it's possible that a crazy client could set se_fchannel.maxreq_sz
> too small, and then we'd get a failure here even when they only sent a
> single sequence.  Such a client gets what it deserves.

  If kernel err out when crazy client sets maxreq_sz to small, 
  only SEQUENCE operation's size will never exceed maxreq_sz.

  According to RFC5661 18.36.3, if client set maxreq_sz too small, 
  the server SHOULD return NFS4ERR_TOOSMALL in the CREATE_SESSION reply.

thanks,
Mi Jinlong