wan: dscc4: add checks for dma mapping errors

The driver does not check if mapping dma memory succeed.
The patch adds the checks and failure handling.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/wan/dscc4.c

@@ -519,22 +519,30 @@ static inline int try_get_rx_skb(struct dscc4_dev_priv *dpriv,
 				 struct net_device *dev)
 {
 	unsigned int dirty = dpriv->rx_dirty%RX_RING_SIZE;
+	struct pci_dev *pdev = dpriv->pci_priv->pdev;
 	struct RxFD *rx_fd = dpriv->rx_fd + dirty;
 	const int len = RX_MAX(HDLC_MAX_MRU);
 	struct sk_buff *skb;
-	int ret = 0;
+	dma_addr_t addr;
 
 	skb = dev_alloc_skb(len);
+	if (!skb)
+		goto err_out;
+
+	skb->protocol = hdlc_type_trans(skb, dev);
+	addr = pci_map_single(pdev, skb->data, len, PCI_DMA_FROMDEVICE);
+	if (pci_dma_mapping_error(pdev, addr))
+		goto err_free_skb;
+
 	dpriv->rx_skbuff[dirty] = skb;
-	if (skb) {
-		skb->protocol = hdlc_type_trans(skb, dev);
-		rx_fd->data = cpu_to_le32(pci_map_single(dpriv->pci_priv->pdev,
-					  skb->data, len, PCI_DMA_FROMDEVICE));
-	} else {
-		rx_fd->data = 0;
-		ret = -1;
-	}
-	return ret;
+	rx_fd->data = cpu_to_le32(addr);
+	return 0;
+
+err_free_skb:
+	dev_kfree_skb_any(skb);
+err_out:
+	rx_fd->data = 0;
+	return -1;
 }
 
 /*
@@ -1145,16 +1153,23 @@ static netdev_tx_t dscc4_start_xmit(struct sk_buff *skb,
 					  struct net_device *dev)
 {
 	struct dscc4_dev_priv *dpriv = dscc4_priv(dev);
-	struct dscc4_pci_priv *ppriv = dpriv->pci_priv;
+	struct pci_dev *pdev = dpriv->pci_priv->pdev;
 	struct TxFD *tx_fd;
+	dma_addr_t addr;
 	int next;
 
+	addr = pci_map_single(pdev, skb->data, skb->len, PCI_DMA_TODEVICE);
+	if (pci_dma_mapping_error(pdev, addr)) {
+		dev_kfree_skb_any(skb);
+		dev->stats.tx_dropped++;
+		return NETDEV_TX_OK;
+	}
+
 	next = dpriv->tx_current%TX_RING_SIZE;
 	dpriv->tx_skbuff[next] = skb;
 	tx_fd = dpriv->tx_fd + next;
 	tx_fd->state = FrameEnd | TO_STATE_TX(skb->len);
-	tx_fd->data = cpu_to_le32(pci_map_single(ppriv->pdev, skb->data, skb->len,
-				     PCI_DMA_TODEVICE));
+	tx_fd->data = cpu_to_le32(addr);
 	tx_fd->complete = 0x00000000;
 	tx_fd->jiffies = jiffies;
 	mb();
@@ -1887,16 +1902,22 @@ static struct sk_buff *dscc4_init_dummy_skb(struct dscc4_dev_priv *dpriv)
 
 	skb = dev_alloc_skb(DUMMY_SKB_SIZE);
 	if (skb) {
+		struct pci_dev *pdev = dpriv->pci_priv->pdev;
 		int last = dpriv->tx_dirty%TX_RING_SIZE;
 		struct TxFD *tx_fd = dpriv->tx_fd + last;
+		dma_addr_t addr;
 
 		skb->len = DUMMY_SKB_SIZE;
 		skb_copy_to_linear_data(skb, version,
 					strlen(version) % DUMMY_SKB_SIZE);
+		addr = pci_map_single(pdev, skb->data, DUMMY_SKB_SIZE,
+				      PCI_DMA_TODEVICE);
+		if (pci_dma_mapping_error(pdev, addr)) {
+			dev_kfree_skb_any(skb);
+			return NULL;
+		}
 		tx_fd->state = FrameEnd | TO_STATE_TX(DUMMY_SKB_SIZE);
-		tx_fd->data = cpu_to_le32(pci_map_single(dpriv->pci_priv->pdev,
-					     skb->data, DUMMY_SKB_SIZE,
-					     PCI_DMA_TODEVICE));
+		tx_fd->data = cpu_to_le32(addr);
 		dpriv->tx_skbuff[last] = skb;
 	}
 	return skb;