nfc: pn533: Fix use-after-free bugs caused by pn532_cmd_timeout

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: nfc: pn533: Fix use-after-free bugs caused by pn532_cmd_timeout 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.

References

• https://git.kernel.org/stable/c/50403ee6daddf0d7a14e9d3b51a377c39a08ec8c
• https://git.kernel.org/stable/c/9c34c33893db7a80d0e4b55c23d3b65e29609cfb
• https://git.kernel.org/stable/c/2c71f5d55a86fd5969428abf525c1ae6b1c7b0f5
• https://git.kernel.org/stable/c/f1e941dbf80a9b8bab0bffbc4cbe41cc7f4c6fb6