Date: Thu, 18 Jan 2018 11:59:33 -0500
From: "J. Bruce Fields" <bfields@redhat.com>
To: Lu Xinyu <luxy.fnst@cn.fujitsu.com>
Cc: linux-nfs@vger.kernel.org
Subject: Re: nfsd: return RESOURCE not GARBAGE_ARGS on too many ops
Message-ID: <20180118165933.GA23587@parsley.fieldses.org>
References: <717a096b-96d6-87d2-9b7f-54bdd182e220@cn.fujitsu.com>
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In-Reply-To: <717a096b-96d6-87d2-9b7f-54bdd182e220@cn.fujitsu.com>
Sender: linux-nfs-owner@vger.kernel.org

On Wed, Jan 17, 2018 at 10:55:52AM +0800, Lu Xinyu wrote:
> Hi Bruce
> 
> Would you consider the patch for merging ?

Thanks for the reminder.  Applying.--b.

> 
> > commit fd9a5e1c4952
> > Author: J. Bruce Fields <bfields@redhat.com>
> > Date:   Wed Nov 15 12:30:27 2017 -0500
> > 
> >     nfsd: return RESOURCE not GARBAGE_ARGS on too many ops
> >     
> >     A client that sends more than a hundred ops in a single compound
> >     currently gets an rpc-level GARBAGE_ARGS error.
> >     
> >     It would be more helpful to return NFS4ERR_RESOURCE, since that gives
> >     the client a better idea how to recover (for example by splitting up the
> >     compound into smaller compounds).
> >     
> >     This is all a bit academic since we've never actually seen a reason for
> >     clients to send such long compounds, but we may as well fix it.
> >     
> >     While we're there, just use NFSD4_MAX_OPS_PER_COMPOUND == 16, the
> >     constant we already use in the 4.1 case, instead of hard-coding 100.
> >     Chances anyone actually uses even 16 ops per compound are small enough
> >     that I think there's a neglible risk or any regression.
> >     
> >     This fixes pynfs test COMP6.
> >     
> >     Reported-by: sunlianwen <sunlw.fnst@cn.fujitsu.com>
> >     Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> > 
> > diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> > index 008ea0b627d0..c9669d75c157 100644
> > --- a/fs/nfsd/nfs4proc.c
> > +++ b/fs/nfsd/nfs4proc.c
> > @@ -1703,6 +1703,9 @@ nfsd4_proc_compound(struct svc_rqst *rqstp)
> >          status = nfserr_minor_vers_mismatch;
> >          if (nfsd_minorversion(args->minorversion, NFSD_TEST) <= 0)
> >                  goto out;
> > +       status = nfserr_resource;
> > +       if (resp->opcnt > NFSD_MAX_OPS_PER_COMPOUND)
> > +               goto out;
> >  
> >          status = nfs41_check_op_ordering(args);
> >          if (status) {
> > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > index 2c61c6b8ae09..5dcd7cb45b2d 100644
> > --- a/fs/nfsd/nfs4xdr.c
> > +++ b/fs/nfsd/nfs4xdr.c
> > @@ -1918,8 +1918,13 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
> >  
> >          if (argp->taglen > NFSD4_MAX_TAGLEN)
> >                  goto xdr_error;
> > -       if (argp->opcnt > 100)
> > -               goto xdr_error;
> > +       /*
> > +        * NFS4ERR_RESOURCE is a more helpful error than GARBAGE_ARGS
> > +        * here, so we return success at the xdr level so that
> > +        * nfsd4_proc can handle this is an NFS-level error.
> > +        */
> > +       if (argp->opcnt > NFSD_MAX_OPS_PER_COMPOUND)
> > +               return 0;
> >  
> >          if (argp->opcnt > ARRAY_SIZE(argp->iops)) {
> >                  argp->ops = kzalloc(argp->opcnt * sizeof(*argp->ops), GFP_KERNEL);
> > 
> > 
> > .
> 
> --
> Lu Xinyu
> --
> 
>