[IFB]: Fix crash on input device removal

The input_device pointer is not refcounted, which means the device may
disappear while packets are queued, causing a crash when ifb passes packets
with a stale skb->dev pointer to netif_rx().

Fix by storing the interface index instead and do a lookup where neccessary.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Jamal Hadi Salim <hadi@cyberus.ca>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 22 deletions

diff --git a/drivers/net/ifb.c b/drivers/net/ifb.c
index ca2b21f9d444..07b4c0d7a75c 100644
--- a/drivers/net/ifb.c
+++ b/drivers/net/ifb.c
@@ -96,17 +96,24 @@ static void ri_tasklet(unsigned long dev)
                 skb->tc_verd = SET_TC_NCLS(skb->tc_verd);
                 stats->tx_packets++;
                 stats->tx_bytes +=skb->len;
+
+                skb->dev = __dev_get_by_index(skb->iif);
+                if (!skb->dev) {
+                        dev_kfree_skb(skb);
+                        stats->tx_dropped++;
+                        break;
+                }
+                skb->iif = _dev->ifindex;
+
                 if (from & AT_EGRESS) {
                         dp->st_rx_frm_egr++;
                         dev_queue_xmit(skb);
                 } else if (from & AT_INGRESS) {
-
                         dp->st_rx_frm_ing++;
+                        skb_pull(skb, skb->dev->hard_header_len);
                         netif_rx(skb);
-                } else {
-                        dev_kfree_skb(skb);
-                        stats->tx_dropped++;
-                }
+                } else
+                        BUG();
         }
 
         if (netif_tx_trylock(_dev)) {
@@ -157,26 +164,10 @@ static int ifb_xmit(struct sk_buff *skb, struct net_device *dev)
         stats->rx_packets++;
         stats->rx_bytes+=skb->len;
 
-        if (!from || !skb->input_dev) {
-dropped:
+        if (!(from & (AT_INGRESS|AT_EGRESS)) || !skb->iif) {
                 dev_kfree_skb(skb);
                 stats->rx_dropped++;
                 return ret;
-        } else {
-                /*
-                 * note we could be going
-                 * ingress -> egress or
-                 * egress -> ingress
-                */
-                skb->dev = skb->input_dev;
-                skb->input_dev = dev;
-                if (from & AT_INGRESS) {
-                        skb_pull(skb, skb->dev->hard_header_len);
-                } else {
-                        if (!(from & AT_EGRESS)) {
-                                goto dropped;
-                        }
-                }
         }
 
         if (skb_queue_len(&dp->rq) >= dev->tx_queue_len) {