can: gs_usb: gs_can_open(): improve error handling

The gs_usb driver handles USB devices with more than 1 CAN channel.
The RX path for all channels share the same bulk endpoint (the
transmitted bulk data encodes the channel number). These per-device
resources are allocated and submitted by the first opened channel.

During this allocation, the resources are either released immediately
in case of a failure or the URBs are anchored. All anchored URBs are
finally killed with gs_usb_disconnect().

Currently, gs_can_open() returns with an error if the allocation of a
URB or a buffer fails. However, if usb_submit_urb() fails, the driver
continues with the URBs submitted so far, even if no URBs were
successfully submitted.

Treat every error as fatal and free all allocated resources
immediately.

Switch to goto-style error handling, to prepare the driver for more
per-device resource allocation.

Cc: stable@vger.kernel.org
Cc: John Whittington <git@jbrengineering.co.uk>
Link: https://lore.kernel.org/all/20230716-gs_usb-fix-time-stamp-counter-v1-1-9017cefcd9d5@pengutronix.deSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/gs_usb.c

@@ -833,6 +833,7 @@ static int gs_can_open(struct net_device *netdev)
 		.mode = cpu_to_le32(GS_CAN_MODE_START),
 	};
 	struct gs_host_frame *hf;
+	struct urb *urb = NULL;
 	u32 ctrlmode;
 	u32 flags = 0;
 	int rc, i;
@@ -856,13 +857,14 @@ static int gs_can_open(struct net_device *netdev)
 
 	if (!parent->active_channels) {
 		for (i = 0; i < GS_MAX_RX_URBS; i++) {
-			struct urb *urb;
 			u8 *buf;
 
 			/* alloc rx urb */
 			urb = usb_alloc_urb(0, GFP_KERNEL);
-			if (!urb)
-				return -ENOMEM;
+			if (!urb) {
+				rc = -ENOMEM;
+				goto out_usb_kill_anchored_urbs;
+			}
 
 			/* alloc rx buffer */
 			buf = kmalloc(dev->parent->hf_size_rx,
@@ -870,8 +872,8 @@ static int gs_can_open(struct net_device *netdev)
 			if (!buf) {
 				netdev_err(netdev,
 					   "No memory left for USB buffer\n");
-				usb_free_urb(urb);
-				return -ENOMEM;
+				rc = -ENOMEM;
+				goto out_usb_free_urb;
 			}
 
 			/* fill, anchor, and submit rx urb */
@@ -894,9 +896,7 @@ static int gs_can_open(struct net_device *netdev)
 				netdev_err(netdev,
 					   "usb_submit failed (err=%d)\n", rc);
 
-				usb_unanchor_urb(urb);
-				usb_free_urb(urb);
-				break;
+				goto out_usb_unanchor_urb;
 			}
 
 			/* Drop reference,
@@ -945,7 +945,8 @@ static int gs_can_open(struct net_device *netdev)
 		if (dev->feature & GS_CAN_FEATURE_HW_TIMESTAMP)
 			gs_usb_timestamp_stop(dev);
 		dev->can.state = CAN_STATE_STOPPED;
-		return rc;
+
+		goto out_usb_kill_anchored_urbs;
 	}
 
 	parent->active_channels++;
@@ -953,6 +954,18 @@ static int gs_can_open(struct net_device *netdev)
 		netif_start_queue(netdev);
 
 	return 0;
+
+out_usb_unanchor_urb:
+	usb_unanchor_urb(urb);
+out_usb_free_urb:
+	usb_free_urb(urb);
+out_usb_kill_anchored_urbs:
+	if (!parent->active_channels)
+		usb_kill_anchored_urbs(&dev->tx_submitted);
+
+	close_candev(netdev);
+
+	return rc;
 }
 
 static int gs_usb_get_state(const struct net_device *netdev,