[3.19.y-ckt stable] Patch "nfs4: limit callback decoding to received bytes" has been added to staging queue

[Kamal Mostafa]

On Tue, 2015-12-15 at 17:26 -0500, Benjamin Coddington wrote:
> Hi Kamal,
> 
> This will break the NFS client's callback channel without Trond's fix
> 756b9b37cfb2e3dc76b2e43a8c097402ac736e07.  It shouldn't be added without
> that one as well.
> 
> Ben

Thanks for the heads-up Ben.  I'll make sure that follow-up fix gets
applied in the same 3.19-stable release.

 -Kamal


> 
> On Tue, 15 Dec 2015, Kamal Mostafa wrote:
> 
> > This is a note to let you know that I have just added a patch titled
> >
> >     nfs4: limit callback decoding to received bytes
> >
> > to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree
> > which can be found at:
> >
> >     http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue
> >
> > This patch is scheduled to be released in version 3.19.8-ckt12.
> >
> > If you, or anyone else, feels it should not be added to this tree, please
> > reply to this email.
> >
> > For more information about the 3.19.y-ckt tree, see
> > https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
> >
> > Thanks.
> > -Kamal
> >
> > ------
> >
> > From 44e003f516dc4407fee82e3f668369a551284ead Mon Sep 17 00:00:00 2001
> > From: Benjamin Coddington <bcodding at redhat.com>
> > Date: Fri, 20 Nov 2015 09:55:30 -0500
> > Subject: nfs4: limit callback decoding to received bytes
> >
> > commit 38b7631fbe42e6e247e9fc9879f961b14a687e3b upstream.
> >
> > A truncated cb_compound request will cause the client to decode null or
> > data from a previous callback for nfs4.1 backchannel case, or uninitialized
> > data for the nfs4.0 case. This is because the path through
> > svc_process_common() advances the request's iov_base and decrements iov_len
> > without adjusting the overall xdr_buf's len field.  That causes
> > xdr_init_decode() to set up the xdr_stream with an incorrect length in
> > nfs4_callback_compound().
> >
> > Fixing this for the nfs4.1 backchannel case first requires setting the
> > correct iov_len and page_len based on the length of received data in the
> > same manner as the nfs4.0 case.
> >
> > Then the request's xdr_buf length can be adjusted for both cases based upon
> > the remaining iov_len and page_len.
> >
> > Signed-off-by: Benjamin Coddington <bcodding at redhat.com>
> > Signed-off-by: Trond Myklebust <trond.myklebust at primarydata.com>
> > Signed-off-by: Kamal Mostafa <kamal at canonical.com>
> > ---
> >  fs/nfs/callback_xdr.c         | 7 +++++--
> >  net/sunrpc/backchannel_rqst.c | 8 ++++++++
> >  net/sunrpc/svc.c              | 1 +
> >  3 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
> > index 02f8d09..1e36635 100644
> > --- a/fs/nfs/callback_xdr.c
> > +++ b/fs/nfs/callback_xdr.c
> > @@ -76,7 +76,8 @@ static __be32 *read_buf(struct xdr_stream *xdr, int nbytes)
> >
> >  	p = xdr_inline_decode(xdr, nbytes);
> >  	if (unlikely(p == NULL))
> > -		printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed!\n");
> > +		printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed "
> > +							"or truncated request.\n");
> >  	return p;
> >  }
> >
> > @@ -892,6 +893,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
> >  	struct cb_compound_hdr_arg hdr_arg = { 0 };
> >  	struct cb_compound_hdr_res hdr_res = { NULL };
> >  	struct xdr_stream xdr_in, xdr_out;
> > +	struct xdr_buf *rq_arg = &rqstp->rq_arg;
> >  	__be32 *p, status;
> >  	struct cb_process_state cps = {
> >  		.drc_status = 0,
> > @@ -903,7 +905,8 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
> >
> >  	dprintk("%s: start\n", __func__);
> >
> > -	xdr_init_decode(&xdr_in, &rqstp->rq_arg, rqstp->rq_arg.head[0].iov_base);
> > +	rq_arg->len = rq_arg->head[0].iov_len + rq_arg->page_len;
> > +	xdr_init_decode(&xdr_in, rq_arg, rq_arg->head[0].iov_base);
> >
> >  	p = (__be32*)((char *)rqstp->rq_res.head[0].iov_base + rqstp->rq_res.head[0].iov_len);
> >  	xdr_init_encode(&xdr_out, &rqstp->rq_res, p);
> > diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
> > index 28504df..b57cee1 100644
> > --- a/net/sunrpc/backchannel_rqst.c
> > +++ b/net/sunrpc/backchannel_rqst.c
> > @@ -308,11 +308,19 @@ void xprt_complete_bc_request(struct rpc_rqst *req, uint32_t copied)
> >  {
> >  	struct rpc_xprt *xprt = req->rq_xprt;
> >  	struct svc_serv *bc_serv = xprt->bc_serv;
> > +	struct xdr_buf *rq_rcv_buf = &req->rq_rcv_buf;
> >
> >  	spin_lock(&xprt->bc_pa_lock);
> >  	list_del(&req->rq_bc_pa_list);
> >  	spin_unlock(&xprt->bc_pa_lock);
> >
> > +	if (copied <= rq_rcv_buf->head[0].iov_len) {
> > +		rq_rcv_buf->head[0].iov_len = copied;
> > +		rq_rcv_buf->page_len = 0;
> > +	} else {
> > +		rq_rcv_buf->page_len = copied - rq_rcv_buf->head[0].iov_len;
> > +	}
> > +
> >  	req->rq_private_buf.len = copied;
> >  	set_bit(RPC_BC_PA_IN_USE, &req->rq_bc_pa_state);
> >
> > diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
> > index 91eaef1..b59b6a7 100644
> > --- a/net/sunrpc/svc.c
> > +++ b/net/sunrpc/svc.c
> > @@ -1361,6 +1361,7 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
> >  	memcpy(&rqstp->rq_addr, &req->rq_xprt->addr, rqstp->rq_addrlen);
> >  	memcpy(&rqstp->rq_arg, &req->rq_rcv_buf, sizeof(rqstp->rq_arg));
> >  	memcpy(&rqstp->rq_res, &req->rq_snd_buf, sizeof(rqstp->rq_res));
> > +	rqstp->rq_arg.len = req->rq_private_buf.len;
> >
> >  	/* reset result send buffer "put" position */
> >  	resv->iov_len = 0;
> > --
> > 1.9.1
> >
> >
>