net: Check L4 header size

net_tx_pkt_build_vheader() inspects TCP header but had no check for
the header size, resulting in an undefined behavior. Check the header
size and drop the packet if the header is too small.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

hw/net/e1000e_core.c

@@ -629,23 +629,30 @@ e1000e_rss_parse_packet(E1000ECore *core,
     info->queue = E1000_RSS_QUEUE(&core->mac[RETA], info->hash);
 }
 
-static void
+static bool
 e1000e_setup_tx_offloads(E1000ECore *core, struct e1000e_tx *tx)
 {
     if (tx->props.tse && tx->cptse) {
-        net_tx_pkt_build_vheader(tx->tx_pkt, true, true, tx->props.mss);
+        if (!net_tx_pkt_build_vheader(tx->tx_pkt, true, true, tx->props.mss)) {
+            return false;
+        }
+
         net_tx_pkt_update_ip_checksums(tx->tx_pkt);
         e1000x_inc_reg_if_not_full(core->mac, TSCTC);
-        return;
+        return true;
     }
 
     if (tx->sum_needed & E1000_TXD_POPTS_TXSM) {
-        net_tx_pkt_build_vheader(tx->tx_pkt, false, true, 0);
+        if (!net_tx_pkt_build_vheader(tx->tx_pkt, false, true, 0)) {
+            return false;
+        }
     }
 
     if (tx->sum_needed & E1000_TXD_POPTS_IXSM) {
         net_tx_pkt_update_ip_hdr_checksum(tx->tx_pkt);
     }
+
+    return true;
 }
 
 static bool
@@ -654,7 +661,9 @@ e1000e_tx_pkt_send(E1000ECore *core, struct e1000e_tx *tx, int queue_index)
     int target_queue = MIN(core->max_queue_num, queue_index);
     NetClientState *queue = qemu_get_subqueue(core->owner_nic, target_queue);
 
-    e1000e_setup_tx_offloads(core, tx);
+    if (!e1000e_setup_tx_offloads(core, tx)) {
+        return false;
+    }
 
     net_tx_pkt_dump(tx->tx_pkt);
 

hw/net/net_tx_pkt.c

@@ -304,10 +304,11 @@ func_exit:
     return rc;
 }
 
-void net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
+bool net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
     bool csum_enable, uint32_t gso_size)
 {
     struct tcp_hdr l4hdr;
+    size_t bytes_read;
     assert(pkt);
 
     /* csum has to be enabled if tso is. */
@@ -328,8 +329,12 @@ void net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
 
     case VIRTIO_NET_HDR_GSO_TCPV4:
     case VIRTIO_NET_HDR_GSO_TCPV6:
-        iov_to_buf(&pkt->vec[NET_TX_PKT_PL_START_FRAG], pkt->payload_frags,
-                   0, &l4hdr, sizeof(l4hdr));
+        bytes_read = iov_to_buf(&pkt->vec[NET_TX_PKT_PL_START_FRAG],
+                                pkt->payload_frags, 0, &l4hdr, sizeof(l4hdr));
+        if (bytes_read < sizeof(l4hdr)) {
+            return false;
+        }
+
         pkt->virt_hdr.hdr_len = pkt->hdr_len + l4hdr.th_off * sizeof(uint32_t);
         pkt->virt_hdr.gso_size = gso_size;
         break;
@@ -354,6 +359,8 @@ void net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
             break;
         }
     }
+
+    return true;
 }
 
 void net_tx_pkt_setup_vlan_header_ex(struct NetTxPkt *pkt,

hw/net/net_tx_pkt.h

@@ -59,9 +59,10 @@ struct virtio_net_hdr *net_tx_pkt_get_vhdr(struct NetTxPkt *pkt);
  * @tso_enable:     TSO enabled
  * @csum_enable:    CSO enabled
  * @gso_size:       MSS size for TSO
+ * @ret:            operation result
  *
  */
-void net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
+bool net_tx_pkt_build_vheader(struct NetTxPkt *pkt, bool tso_enable,
     bool csum_enable, uint32_t gso_size);
 
 /**

hw/net/vmxnet3.c

@@ -440,19 +440,19 @@ vmxnet3_setup_tx_offloads(VMXNET3State *s)
 {
     switch (s->offload_mode) {
     case VMXNET3_OM_NONE:
-        net_tx_pkt_build_vheader(s->tx_pkt, false, false, 0);
-        break;
+        return net_tx_pkt_build_vheader(s->tx_pkt, false, false, 0);
 
     case VMXNET3_OM_CSUM:
-        net_tx_pkt_build_vheader(s->tx_pkt, false, true, 0);
         VMW_PKPRN("L4 CSO requested\n");
-        break;
+        return net_tx_pkt_build_vheader(s->tx_pkt, false, true, 0);
 
     case VMXNET3_OM_TSO:
-        net_tx_pkt_build_vheader(s->tx_pkt, true, true,
-            s->cso_or_gso_size);
-        net_tx_pkt_update_ip_checksums(s->tx_pkt);
         VMW_PKPRN("GSO offload requested.");
+        if (!net_tx_pkt_build_vheader(s->tx_pkt, true, true,
+            s->cso_or_gso_size)) {
+            return false;
+        }
+        net_tx_pkt_update_ip_checksums(s->tx_pkt);
         break;
 
     default: