Hi! I did some debugging on this https://syzkaller.appspot.com/bug?id=3ea507fb3c47426497b52bd82b8ef0dd5b6cc7ee and, I believe, I recognized the problem. The problem appears in case of ath9k_htc_hw_init() fail. In case of this fail all tx_buf->urb krefs will be initialized to 1, but in free function: static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb *hif_dev) .... static void ath9k_hif_usb_dealloc_tx_urbs(struct hif_device_usb *hif_dev) { ... list_for_each_entry_safe(tx_buf, tx_buf_tmp, &hif_dev->tx.tx_buf, list) { usb_get_urb(tx_buf->urb); ... usb_free_urb(tx_buf->urb); ... } Krefs are incremented and then decremented, that means urbs won't be freed. I found your patch and I can't properly understand why You added usb_get_urb(tx_buf->urb). Can You explain please, I believe this will help me or somebody to fix this ussue :) With regards, Pavel Skripkin