xen-netback: avoid allocating variable size array on stack

Tune xen_netbk_count_requests to not touch working array beyond limit, so that
we can make working array size constant.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 2 deletions

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index c44772d6bba0..ce8109f7d56f 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -934,11 +934,14 @@ static int netbk_count_requests(struct xenvif *vif,
         RING_IDX cons = vif->tx.req_cons;
         int slots = 0;
         int drop_err = 0;
+        int more_data;
 
         if (!(first->flags & XEN_NETTXF_more_data))
                 return 0;
 
         do {
+                struct xen_netif_tx_request dropped_tx = { 0 };
+
                 if (slots >= work_to_do) {
                         netdev_err(vif->dev,
                                    "Asked for %d slots but exceeds this limit\n",
@@ -972,6 +975,9 @@ static int netbk_count_requests(struct xenvif *vif,
                         drop_err = -E2BIG;
                 }
 
+                if (drop_err)
+                        txp = &dropped_tx;
+
                 memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
                        sizeof(*txp));
 
@@ -1001,7 +1007,13 @@ static int netbk_count_requests(struct xenvif *vif,
                         netbk_fatal_tx_err(vif);
                         return -EINVAL;
                 }
-        } while ((txp++)->flags & XEN_NETTXF_more_data);
+
+                more_data = txp->flags & XEN_NETTXF_more_data;
+
+                if (!drop_err)
+                        txp++;
+
+        } while (more_data);
 
         if (drop_err) {
                 netbk_tx_err(vif, first, cons + slots);
@@ -1408,7 +1420,7 @@ static unsigned xen_netbk_tx_build_gops(struct xen_netbk *netbk)
                 !list_empty(&netbk->net_schedule_list)) {
                 struct xenvif *vif;
                 struct xen_netif_tx_request txreq;
-                struct xen_netif_tx_request txfrags[max_skb_slots];
+                struct xen_netif_tx_request txfrags[XEN_NETIF_NR_SLOTS_MIN];
                 struct page *page;
                 struct xen_netif_extra_info extras[XEN_NETIF_EXTRA_TYPE_MAX-1];
                 u16 pending_idx;