[PATCH 3.2 22/70] xen-netback: use RING_COPY_REQUEST() throughout

[Ben Hutchings <ben@decadent.org.uk>]

3.2.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: David Vrabel <david.vrabel@citrix.com>

commit 68a33bfd8403e4e22847165d149823a2e0e67c9c upstream.

Instead of open-coding memcpy()s and directly accessing Tx and Rx
requests, use the new RING_COPY_REQUEST() that ensures the local copy
is correct.

This is more than is strictly necessary for guest Rx requests since
only the id and gref fields are used and it is harmless if the
frontend modifies these.

This is part of XSA155.

Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
[bwh: Backported to 3.2:
 - s/queue/vif/g
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/net/xen-netback/netback.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -406,17 +406,17 @@ static struct netbk_rx_meta *get_next_rx
 						struct netrx_pending_operations *npo)
 {
 	struct netbk_rx_meta *meta;
-	struct xen_netif_rx_request *req;
+	struct xen_netif_rx_request req;
 
-	req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
+	RING_COPY_REQUEST(&vif->rx, vif->rx.req_cons++, &req);
 
 	meta = npo->meta + npo->meta_prod++;
 	meta->gso_size = 0;
 	meta->size = 0;
-	meta->id = req->id;
+	meta->id = req.id;
 
 	npo->copy_off = 0;
-	npo->copy_gref = req->gref;
+	npo->copy_gref = req.gref;
 
 	return meta;
 }
@@ -518,7 +518,7 @@ static int netbk_gop_skb(struct sk_buff
 	struct xenvif *vif = netdev_priv(skb->dev);
 	int nr_frags = skb_shinfo(skb)->nr_frags;
 	int i;
-	struct xen_netif_rx_request *req;
+	struct xen_netif_rx_request req;
 	struct netbk_rx_meta *meta;
 	unsigned char *data;
 	int head = 1;
@@ -528,14 +528,14 @@ static int netbk_gop_skb(struct sk_buff
 
 	/* Set up a GSO prefix descriptor, if necessary */
 	if (skb_shinfo(skb)->gso_size && vif->gso_prefix) {
-		req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
+		RING_COPY_REQUEST(&vif->rx, vif->rx.req_cons++, &req);
 		meta = npo->meta + npo->meta_prod++;
 		meta->gso_size = skb_shinfo(skb)->gso_size;
 		meta->size = 0;
-		meta->id = req->id;
+		meta->id = req.id;
 	}
 
-	req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
+	RING_COPY_REQUEST(&vif->rx, vif->rx.req_cons++, &req);
 	meta = npo->meta + npo->meta_prod++;
 
 	if (!vif->gso_prefix)
@@ -544,9 +544,9 @@ static int netbk_gop_skb(struct sk_buff
 		meta->gso_size = 0;
 
 	meta->size = 0;
-	meta->id = req->id;
+	meta->id = req.id;
 	npo->copy_off = 0;
-	npo->copy_gref = req->gref;
+	npo->copy_gref = req.gref;
 
 	data = skb->data;
 	while (data < skb_tail_pointer(skb)) {
@@ -890,7 +890,7 @@ static void netbk_tx_err(struct xenvif *
 		make_tx_response(vif, txp, XEN_NETIF_RSP_ERROR);
 		if (cons == end)
 			break;
-		txp = RING_GET_REQUEST(&vif->tx, cons++);
+		RING_COPY_REQUEST(&vif->tx, cons++, txp);
 	} while (1);
 	vif->tx.req_cons = cons;
 	xen_netbk_check_rx_xenvif(vif);
@@ -957,8 +957,7 @@ static int netbk_count_requests(struct x
 		if (drop_err)
 			txp = &dropped_tx;
 
-		memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
-		       sizeof(*txp));
+		RING_COPY_REQUEST(&vif->tx, cons + slots, txp);
 
 		/* If the guest submitted a frame >= 64 KiB then
 		 * first->size overflowed and following slots will
@@ -1246,8 +1245,7 @@ static int xen_netbk_get_extras(struct x
 			return -EBADR;
 		}
 
-		memcpy(&extra, RING_GET_REQUEST(&vif->tx, cons),
-		       sizeof(extra));
+		RING_COPY_REQUEST(&vif->tx, cons, &extra);
 		if (unlikely(!extra.type ||
 			     extra.type >= XEN_NETIF_EXTRA_TYPE_MAX)) {
 			vif->tx.req_cons = ++cons;
@@ -1442,7 +1440,7 @@ static unsigned xen_netbk_tx_build_gops(
 
 		idx = vif->tx.req_cons;
 		rmb(); /* Ensure that we see the request before we copy it. */
-		memcpy(&txreq, RING_GET_REQUEST(&vif->tx, idx), sizeof(txreq));
+		RING_COPY_REQUEST(&vif->tx, idx, &txreq);
 
 		/* Credit-based scheduling. */
 		if (txreq.size > vif->remaining_credit &&