static int ath10k_usb_hif_tx_sg(struct ath10k *ar, u8 pipe_id,
				struct ath10k_hif_sg_item *items, int n_items)
{
	struct ath10k_usb *ar_usb = ath10k_usb_priv(ar);
	struct ath10k_usb_pipe *pipe = &ar_usb->pipes[pipe_id];
	struct ath10k_urb_context *urb_context;
	struct sk_buff *skb;
	struct urb *urb;
	int ret, i;

	for (i = 0; i < n_items; i++) {
		urb_context = ath10k_usb_alloc_urb_from_pipe(pipe);
		if (!urb_context) {
			ret = -ENOMEM;
			goto err;
		}

		skb = items[i].transfer_context;
		urb_context->skb = skb;

		urb = usb_alloc_urb(0, GFP_ATOMIC);
		if (!urb) {
			ret = -ENOMEM;
			goto err_free_urb_to_pipe;
		}

		usb_fill_bulk_urb(urb,
				  ar_usb->udev,
				  pipe->usb_pipe_handle,
				  skb->data,
				  skb->len,
				  ath10k_usb_transmit_complete, urb_context);

		if (!(skb->len % pipe->max_packet_size)) {
			/* hit a max packet boundary on this pipe */
			urb->transfer_flags |= URB_ZERO_PACKET;
		}

		usb_anchor_urb(urb, &pipe->urb_submitted);
		ret = usb_submit_urb(urb, GFP_ATOMIC);
		if (ret) {
			ath10k_dbg(ar, ATH10K_DBG_USB_BULK,
				   "usb bulk transmit failed: %d\n", ret);
			usb_unanchor_urb(urb);
			usb_free_urb(urb);
			ret = -EINVAL;
			goto err_free_urb_to_pipe;
		}

		usb_free_urb(urb);
	}

	return 0;

err_free_urb_to_pipe:
	ath10k_usb_free_urb_to_pipe(urb_context->pipe, urb_context);
err:
	return ret;
}
The software does not sufficiently track and release allocated memory after it has been used, which slowly consumes remaining memory.