On Tue, 2 Apr 2024 18:38:08 +0300
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
Hi Andy,
> The removal of the last MAX3100 device triggers the removal of
> the driver. However, code doesn't update the respective global
> variable and after insmod — rmmod — insmod cycle the kernel
> oopses:
>
> max3100 spi-PRP0001:01: max3100_probe: adding port 0
> BUG: kernel NULL pointer dereference, address: 0000000000000408
> ...
> RIP: 0010:serial_core_register_port+0xa0/0x840
> ...
> max3100_probe+0x1b6/0x280 [max3100]
> spi_probe+0x8d/0xb0
>
> Update the actual state so next time UART driver will be registered
> again.
>
> Fixes: 7831d56b0a35 ("tty: MAX3100")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> ---
> drivers/tty/serial/max3100.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/drivers/tty/serial/max3100.c b/drivers/tty/serial/max3100.c
> index 45022f2909f0..efe26f6d5ebf 100644
> --- a/drivers/tty/serial/max3100.c
> +++ b/drivers/tty/serial/max3100.c
> @@ -841,6 +841,7 @@ static void max3100_remove(struct spi_device *spi)
> }
> pr_debug("removing max3100 driver\n");
> uart_unregister_driver(&max3100_uart_driver);
> + uart_driver_registered = 0;
At the beginning of the probe function, we have:
-----------------------
if (!uart_driver_registered) {
uart_driver_registered = 1;
retval = uart_register_driver(&max3100_uart_driver);
if (retval) {
printk(KERN_ERR "Couldn't register max3100 uart
driver\n"); mutex_unlock(&max3100s_lock);
return retval;
...
-----------------------
If uart_register_driver() fails, uart_driver_registered would still be
true and would it prevent any other subsequent devices from being
properly registered? If yes, then maybe "uart_driver_registered = 1"
should be set only after a sucessfull call to uart_register_driver()?
Hugo.
>
> mutex_unlock(&max3100s_lock);
> }
> --
> 2.43.0.rc1.1.gbec44491f096
>
>
