can: esd_usb2: fix memory leak

In esd_usb2_setup_rx_urbs() MAX_RX_URBS coherent buffers are allocated
and there is nothing, that frees them:

1) In callback function the urb is resubmitted and that's all
2) In disconnect function urbs are simply killed, but URB_FREE_BUFFER
   is not set (see esd_usb2_setup_rx_urbs) and this flag cannot be used
   with coherent buffers.

So, all allocated buffers should be freed with usb_free_coherent()
explicitly.

Side note: This code looks like a copy-paste of other can drivers. The
same patch was applied to mcba_usb driver and it works nice with real
hardware. There is no change in functionality, only clean-up code for
coherent buffers.

Fixes: 96d8e903 ("can: Add driver for esd CAN-USB/2 device")
Link: https://lore.kernel.org/r/b31b096926dcb35998ad0271aac4b51770ca7cc8.1627404470.git.paskripkin@gmail.com
Cc: linux-stable <stable@vger.kernel.org>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/esd_usb2.c

@@ -195,6 +195,8 @@ struct esd_usb2 {
 	int net_count;
 	u32 version;
 	int rxinitdone;
+	void *rxbuf[MAX_RX_URBS];
+	dma_addr_t rxbuf_dma[MAX_RX_URBS];
 };
 
 struct esd_usb2_net_priv {
@@ -545,6 +547,7 @@ static int esd_usb2_setup_rx_urbs(struct esd_usb2 *dev)
 	for (i = 0; i < MAX_RX_URBS; i++) {
 		struct urb *urb = NULL;
 		u8 *buf = NULL;
+		dma_addr_t buf_dma;
 
 		/* create a URB, and a buffer for it */
 		urb = usb_alloc_urb(0, GFP_KERNEL);
@@ -554,7 +557,7 @@ static int esd_usb2_setup_rx_urbs(struct esd_usb2 *dev)
 		}
 
 		buf = usb_alloc_coherent(dev->udev, RX_BUFFER_SIZE, GFP_KERNEL,
-					 &urb->transfer_dma);
+					 &buf_dma);
 		if (!buf) {
 			dev_warn(dev->udev->dev.parent,
 				 "No memory left for USB buffer\n");
@@ -562,6 +565,8 @@ static int esd_usb2_setup_rx_urbs(struct esd_usb2 *dev)
 			goto freeurb;
 		}
 
+		urb->transfer_dma = buf_dma;
+
 		usb_fill_bulk_urb(urb, dev->udev,
 				  usb_rcvbulkpipe(dev->udev, 1),
 				  buf, RX_BUFFER_SIZE,
@@ -574,8 +579,12 @@ static int esd_usb2_setup_rx_urbs(struct esd_usb2 *dev)
 			usb_unanchor_urb(urb);
 			usb_free_coherent(dev->udev, RX_BUFFER_SIZE, buf,
 					  urb->transfer_dma);
+			goto freeurb;
 		}
 
+		dev->rxbuf[i] = buf;
+		dev->rxbuf_dma[i] = buf_dma;
+
 freeurb:
 		/* Drop reference, USB core will take care of freeing it */
 		usb_free_urb(urb);
@@ -663,6 +672,11 @@ static void unlink_all_urbs(struct esd_usb2 *dev)
 	int i, j;
 
 	usb_kill_anchored_urbs(&dev->rx_submitted);
+
+	for (i = 0; i < MAX_RX_URBS; ++i)
+		usb_free_coherent(dev->udev, RX_BUFFER_SIZE,
+				  dev->rxbuf[i], dev->rxbuf_dma[i]);
+
 	for (i = 0; i < dev->net_count; i++) {
 		priv = dev->nets[i];
 		if (priv) {