xen-netback: BUG_ON in xenvif_rx_action() not catching overflow

[cascardo/linux.git] / drivers / net / xen-netback / netback.c

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index e5284bc..cd0bd95 100644 (file)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -192,8 +192,8 @@ static bool start_new_rx_buffer(int offset, unsigned long size, int head)
         * into multiple copies tend to give large frags their
         * own buffers as before.
         */
-       if ((offset + size > MAX_BUFFER_OFFSET) &&
-           (size <= MAX_BUFFER_OFFSET) && offset && !head)
+       BUG_ON(size > MAX_BUFFER_OFFSET);
+       if ((offset + size > MAX_BUFFER_OFFSET) && offset && !head)
                return true;
 
        return false;
@@ -240,7 +240,7 @@ static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
        struct gnttab_copy *copy_gop;
        struct xenvif_rx_meta *meta;
        unsigned long bytes;
-       int gso_type;
+       int gso_type = XEN_NETIF_GSO_TYPE_NONE;
 
        /* Data must not cross a page boundary. */
        BUG_ON(size + offset > PAGE_SIZE<<compound_order(page));
@@ -299,12 +299,12 @@ static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
                }
 
                /* Leave a gap for the GSO descriptor. */
-               if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
-                       gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
-               else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
-                       gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
-               else
-                       gso_type = XEN_NETIF_GSO_TYPE_NONE;
+               if (skb_is_gso(skb)) {
+                       if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+                               gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+                       else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+                               gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
+               }
 
                if (*head && ((1 << gso_type) & vif->gso_mask))
                        vif->rx.req_cons++;
@@ -338,19 +338,15 @@ static int xenvif_gop_skb(struct sk_buff *skb,
        int head = 1;
        int old_meta_prod;
        int gso_type;
-       int gso_size;
 
        old_meta_prod = npo->meta_prod;
 
-       if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
-               gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
-               gso_size = skb_shinfo(skb)->gso_size;
-       } else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) {
-               gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
-               gso_size = skb_shinfo(skb)->gso_size;
-       } else {
-               gso_type = XEN_NETIF_GSO_TYPE_NONE;
-               gso_size = 0;
+       gso_type = XEN_NETIF_GSO_TYPE_NONE;
+       if (skb_is_gso(skb)) {
+               if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+                       gso_type = XEN_NETIF_GSO_TYPE_TCPV4;
+               else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+                       gso_type = XEN_NETIF_GSO_TYPE_TCPV6;
        }
 
        /* Set up a GSO prefix descriptor, if necessary */
@@ -358,7 +354,7 @@ static int xenvif_gop_skb(struct sk_buff *skb,
                req = RING_GET_REQUEST(&vif->rx, vif->rx.req_cons++);
                meta = npo->meta + npo->meta_prod++;
                meta->gso_type = gso_type;
-               meta->gso_size = gso_size;
+               meta->gso_size = skb_shinfo(skb)->gso_size;
                meta->size = 0;
                meta->id = req->id;
        }
@@ -368,7 +364,7 @@ static int xenvif_gop_skb(struct sk_buff *skb,
 
        if ((1 << gso_type) & vif->gso_mask) {
                meta->gso_type = gso_type;
-               meta->gso_size = gso_size;
+               meta->gso_size = skb_shinfo(skb)->gso_size;
        } else {
                meta->gso_type = XEN_NETIF_GSO_TYPE_NONE;
                meta->gso_size = 0;
@@ -486,6 +482,8 @@ static void xenvif_rx_action(struct xenvif *vif)
 
        while ((skb = skb_dequeue(&vif->rx_queue)) != NULL) {
                RING_IDX max_slots_needed;
+               RING_IDX old_req_cons;
+               RING_IDX ring_slots_used;
                int i;
 
                /* We need a cheap worse case estimate for the number of
@@ -497,11 +495,31 @@ static void xenvif_rx_action(struct xenvif *vif)
                                                PAGE_SIZE);
                for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
                        unsigned int size;
+                       unsigned int offset;
+
                        size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
-                       max_slots_needed += DIV_ROUND_UP(size, PAGE_SIZE);
+                       offset = skb_shinfo(skb)->frags[i].page_offset;
+
+                       /* For a worse-case estimate we need to factor in
+                        * the fragment page offset as this will affect the
+                        * number of times xenvif_gop_frag_copy() will
+                        * call start_new_rx_buffer().
+                        */
+                       max_slots_needed += DIV_ROUND_UP(offset + size,
+                                                        PAGE_SIZE);
                }
-               if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||
-                   skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+
+               /* To avoid the estimate becoming too pessimal for some
+                * frontends that limit posted rx requests, cap the estimate
+                * at MAX_SKB_FRAGS.
+                */
+               if (max_slots_needed > MAX_SKB_FRAGS)
+                       max_slots_needed = MAX_SKB_FRAGS;
+
+               /* We may need one more slot for GSO metadata */
+               if (skb_is_gso(skb) &&
+                  (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||
+                   skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))
                        max_slots_needed++;
 
                /* If the skb may not fit then bail out now */
@@ -514,8 +532,12 @@ static void xenvif_rx_action(struct xenvif *vif)
                        vif->rx_last_skb_slots = 0;
 
                sco = (struct skb_cb_overlay *)skb->cb;
+
+               old_req_cons = vif->rx.req_cons;
                sco->meta_slots_used = xenvif_gop_skb(skb, &npo);
-               BUG_ON(sco->meta_slots_used > max_slots_needed);
+               ring_slots_used = vif->rx.req_cons - old_req_cons;
+
+               BUG_ON(ring_slots_used > max_slots_needed);
 
                __skb_queue_tail(&rxq, skb);
        }