linux-kernel - Re: [PATCH] nfs: fix bitmap decoder to handle a 3rd word

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Message-ID: <c1d69b024d2a60d2a10e4211c2cbe565ca0e23fb.camel@kernel.org>
Date: Wed, 21 Aug 2024 11:01:45 -0400
From: Jeff Layton <jlayton@...nel.org>
To: Trond Myklebust <trondmy@...merspace.com>, "anna@...nel.org"
	 <anna@...nel.org>, Lance Shelton <Lance.Shelton@...merspace.com>
Cc: "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>, 
 "linux-kernel@...r.kernel.org"
	 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] nfs: fix bitmap decoder to handle a 3rd word

On Wed, 2024-08-21 at 14:58 +0000, Trond Myklebust wrote:
> On Wed, 2024-08-21 at 08:16 -0400, Jeff Layton wrote:
> > It only decodes the first two words at this point. Have it decode the
> > third word as well. Without this, the client doesn't send delegated
> > timestamps in the CB_GETATTR response.
> > 
> > Fixes: 43df7110f4a9 ("NFSv4: Add CB_GETATTR support for delegated
> > attributes")
> > Signed-off-by: Jeff Layton <jlayton@...nel.org>
> > ---
> > Found this while working on the delstid patches for nfsd.
> > ---
> >  fs/nfs/callback_xdr.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
> > index 29c49a7e5fe1..246470306172 100644
> > --- a/fs/nfs/callback_xdr.c
> > +++ b/fs/nfs/callback_xdr.c
> > @@ -118,7 +118,9 @@ static __be32 decode_bitmap(struct xdr_stream
> > *xdr, uint32_t *bitmap)
> >  	if (likely(attrlen > 0))
> >  		bitmap[0] = ntohl(*p++);
> >  	if (attrlen > 1)
> > -		bitmap[1] = ntohl(*p);
> > +		bitmap[1] = ntohl(*p++);
> > +	if (attrlen > 2)
> > +		bitmap[2] = ntohl(*p);
> >  	return 0;
> >  }
> >  
> > 
> > ---
> > base-commit: b311c1b497e51a628aa89e7cb954481e5f9dced2
> > change-id: 20240821-nfs-6-11-188bb4e1f1dd
> > 
> > Best regards,
> 
> Why do we need this? I'm not really understanding which callback
> attributes we'd want to return in that range.
> 

(note that there is a v2 that fixes a potential buffer overrun with
this change. We'll want that one)

FATTR4_WORD2_TIME_DELEG_ACCESS and FATTR4_WORD2_TIME_DELEG_MODIFY. 
43df7110f4a90 added support for those, but the client doesn't see the
server's request for them without this change.

-- 
Jeff Layton <jlayton@...nel.org>