[PATCH 3.16.y-ckt 026/128] SUNRPC: Fix callback channel

[Luis Henriques]

3.16.7-ckt23 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>

commit 756b9b37cfb2e3dc76b2e43a8c097402ac736e07 upstream.

The NFSv4.1 callback channel is currently broken because the receive
message will keep shrinking because the backchannel receive buffer size
never gets reset.
The easiest solution to this problem is instead of changing the receive
buffer, to rather adjust the copied request.

Fixes: 38b7631fbe42 ("nfs4: limit callback decoding to received bytes")
Cc: Benjamin Coddington <bcodding@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 fs/nfs/callback_xdr.c         |  7 ++-----
 net/sunrpc/backchannel_rqst.c |  8 --------
 net/sunrpc/svc.c              | 12 ++++++++++++
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/fs/nfs/callback_xdr.c b/fs/nfs/callback_xdr.c
index 1e366354a193..02f8d09e119f 100644
--- a/fs/nfs/callback_xdr.c
+++ b/fs/nfs/callback_xdr.c
@@ -76,8 +76,7 @@ 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 "
-							"or truncated request.\n");
+		printk(KERN_WARNING "NFS: NFSv4 callback reply buffer overflowed!\n");
 	return p;
 }
 
@@ -893,7 +892,6 @@ 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,
@@ -905,8 +903,7 @@ static __be32 nfs4_callback_compound(struct svc_rqst *rqstp, void *argp, void *r
 
 	dprintk("%s: start\n", __func__);
 
-	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);
+	xdr_init_decode(&xdr_in, &rqstp->rq_arg, rqstp->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 d7b049be631e..ca9ff71134f9 100644
--- a/net/sunrpc/backchannel_rqst.c
+++ b/net/sunrpc/backchannel_rqst.c
@@ -308,19 +308,11 @@ 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 5597f6b85ea5..78c809c1f819 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1358,7 +1358,19 @@ 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));
+
+	/* Adjust the argument buffer length */
 	rqstp->rq_arg.len = req->rq_private_buf.len;
+	if (rqstp->rq_arg.len <= rqstp->rq_arg.head[0].iov_len) {
+		rqstp->rq_arg.head[0].iov_len = rqstp->rq_arg.len;
+		rqstp->rq_arg.page_len = 0;
+	} else if (rqstp->rq_arg.len <= rqstp->rq_arg.head[0].iov_len +
+			rqstp->rq_arg.page_len)
+		rqstp->rq_arg.page_len = rqstp->rq_arg.len -
+			rqstp->rq_arg.head[0].iov_len;
+	else
+		rqstp->rq_arg.len = rqstp->rq_arg.head[0].iov_len +
+			rqstp->rq_arg.page_len;
 
 	/* reset result send buffer "put" position */
 	resv->iov_len = 0;