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

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Message-ID: <89caed01e51c2ba58c3cddc5f335946dac82bd63.camel@hammerspace.com>
Date: Wed, 21 Aug 2024 15:53:38 +0000
From: Trond Myklebust <trondmy@...merspace.com>
To: "anna@...nel.org" <anna@...nel.org>, Lance Shelton
	<Lance.Shelton@...merspace.com>, "jlayton@...nel.org" <jlayton@...nel.org>
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 15:37 +0000, Trond Myklebust wrote:
> On Wed, 2024-08-21 at 11:01 -0400, Jeff Layton wrote:
> > 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.
> > 
> 
> D'oh! Acked...
> 

Sorry. I mean Ack for the v2 that also fixes the resulting potential
for an array overflow in decode_recallany_args.

-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com