Broadcom CNIC core network driver: fix mem leak on allocation failures in cnic_alloc_uio_rings()

We are leaking memory in drivers/net/cnic.c::cnic_alloc_uio_rings() if
either of the calls to dma_alloc_coherent() fail. This patch fixes it by
freeing both the memory allocated with kzalloc() and memory allocated with
previous calls to dma_alloc_coherent() when there's a failure.

Thanks to  Joe Perches <joe@perches.com>  for suggesting a better
implementation than my initial version.
Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Acked-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/cnic.c

@@ -940,7 +940,7 @@ static int cnic_alloc_uio_rings(struct cnic_dev *dev, int pages)
 					   &udev->l2_ring_map,
 					   GFP_KERNEL | __GFP_COMP);
 	if (!udev->l2_ring)
-		return -ENOMEM;
+		goto err_udev;
 
 	udev->l2_buf_size = (cp->l2_rx_ring_size + 1) * cp->l2_single_buf_size;
 	udev->l2_buf_size = PAGE_ALIGN(udev->l2_buf_size);
@@ -948,7 +948,7 @@ static int cnic_alloc_uio_rings(struct cnic_dev *dev, int pages)
 					  &udev->l2_buf_map,
 					  GFP_KERNEL | __GFP_COMP);
 	if (!udev->l2_buf)
-		return -ENOMEM;
+		goto err_dma;
 
 	write_lock(&cnic_dev_lock);
 	list_add(&udev->list, &cnic_udev_list);
@@ -959,6 +959,12 @@ static int cnic_alloc_uio_rings(struct cnic_dev *dev, int pages)
 	cp->udev = udev;
 
 	return 0;
+ err_dma:
+	dma_free_coherent(&udev->pdev->dev, udev->l2_ring_size,
+			  udev->l2_ring, udev->l2_ring_map);
+ err_udev:
+	kfree(udev);
+	return -ENOMEM;
 }
 
 static int cnic_init_uio(struct cnic_dev *dev)