[bug report] Bluetooth: btusb: mediatek: add MediaTek devcoredump support

[Dan Carpenter]

Hello Jing Cai,

The patch 872f8c253cb9: "Bluetooth: btusb: mediatek: add MediaTek
devcoredump support" from Jun 29, 2023, leads to the following Smatch
static checker warning:

	drivers/bluetooth/btmtk.c:409 btmtk_process_coredump()
	error: double free of 'skb'

drivers/bluetooth/btmtk.c
   381                  if (err < 0)
   382                          break;
   383                  data->cd_info.cnt = 0;
   384  
   385                  /* It is supposed coredump can be done within 5 seconds */
   386                  schedule_delayed_work(&hdev->dump.dump_timeout,
   387                                        msecs_to_jiffies(5000));
   388                  fallthrough;
   389          case HCI_DEVCOREDUMP_ACTIVE:
   390          default:
   391                  err = hci_devcd_append(hdev, skb);

hci_devcd_append() free skb on error

   392                  if (err < 0)
   393                          break;
   394                  data->cd_info.cnt++;
   395  
   396                  /* Mediatek coredump data would be more than MTK_COREDUMP_NUM */
   397                  if (data->cd_info.cnt > MTK_COREDUMP_NUM &&
   398                      skb->len > sizeof(MTK_COREDUMP_END) &&
   399                      !memcmp((char *)&skb->data[skb->len - sizeof(MTK_COREDUMP_END)],
   400                              MTK_COREDUMP_END, sizeof(MTK_COREDUMP_END) - 1)) {
   401                          bt_dev_info(hdev, "Mediatek coredump end");
   402                          hci_devcd_complete(hdev);
   403                  }
   404  
   405                  break;
   406          }
   407  
   408          if (err < 0)
   409                  kfree_skb(skb);

double free

   410  
   411          return err;
   412  }

regards,
dan carpenter