When the pn532 uart device is detaching, the pn532_uart_remove()
is called. But there are no functions in pn532_uart_remove() that
could delete the cmd_timeout timer, which will cause use-after-free
bugs. The process is shown below:
(thread 1) | (thread 2)
| pn532_uart_send_frame
pn532_uart_remove | mod_timer(&pn532->cmd_timeout,...)
... | (wait a time)
kfree(pn532) //FREE | pn532_cmd_timeout
| pn532_uart_send_frame
| pn532->... //USE
This patch adds del_timer_sync() in pn532_uart_remove() in order to
prevent the use-after-free bugs. What's more, the pn53x_unregister_nfc()
is well synchronized, it sets nfc_dev->shutting_down to true and there
are no syscalls could restart the cmd_timeout timer.
Fixes: c656aa4c27 ("nfc: pn533: add UART phy driver")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
f1e941dbf8