CVE-2023-53176

In the Linux kernel, the following vulnerability has been resolved:

serial: 8250: Reinit port->pm on port specific driver unbind

When we unbind a serial port hardware specific 8250 driver, the generic serial8250 driver takes over the port. After that we see an oops about 10 seconds later. This can produce the following at least on some TI SoCs:

Unhandled fault: imprecise external abort (0x1406) Internal error: : 1406 [#1] SMP ARM

Turns out that we may still have the serial port hardware specific driver port->pm in use, and serial8250_pm() tries to call it after the port specific driver is gone:

serial8250pm [8250base] from uartchangepm+0x54/0x8c [serialbase] uartchangepm [serialbase] from uarthangup+0x154/0x198 [serialbase] uarthangup [serialbase] from __tty_hangup.part.0+0x328/0x37c __ttyhangup.part.0 from disassociatectty+0x154/0x20c disassociatectty from doexit+0x744/0xaac do_exit from dogroupexit+0x40/0x8c dogroupexit from __wakeupparent+0x0/0x1c

Let's fix the issue by calling serial8250setdefaults() in serial8250unregisterport(). This will set the port back to using the serial8250 default functions, and sets the port->pm to point to serial8250_pm.