[v1] serial: max3100: Put into shape

[PATCH v1 02/16] serial: max3100: Update uart_driver_registered on driver removal

Posted by Andy Shevchenko 1 year, 10 months ago

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@linux.intel.com>
---
 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;
 
 	mutex_unlock(&max3100s_lock);
 }
-- 
2.43.0.rc1.1.gbec44491f096

Re: [PATCH v1 02/16] serial: max3100: Update uart_driver_registered on driver removal

Posted by Hugo Villeneuve 1 year, 10 months ago

On Tue,  2 Apr 2024 18:38:08 +0300
Andy Shevchenko <andriy.shevchenko@linux.intel.com> 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@linux.intel.com>
> ---
>  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
> 
>

Re: [PATCH v1 02/16] serial: max3100: Update uart_driver_registered on driver removal

Posted by Andy Shevchenko 1 year, 10 months ago

On Tue, Apr 02, 2024 at 01:18:27PM -0400, Hugo Villeneuve wrote:
> On Tue,  2 Apr 2024 18:38:08 +0300
> Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

...

> >  	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()?

Looks like yet another issue here (however I haven't hit it so far).
I guess I can combine both fixes.  What do you think?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v1 02/16] serial: max3100: Update uart_driver_registered on driver removal

Posted by Hugo Villeneuve 1 year, 10 months ago

On Tue, 2 Apr 2024 20:31:50 +0300
Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:

> On Tue, Apr 02, 2024 at 01:18:27PM -0400, Hugo Villeneuve wrote:
> > On Tue,  2 Apr 2024 18:38:08 +0300
> > Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> 
> ...
> 
> > >  	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()?
> 
> Looks like yet another issue here (however I haven't hit it so far).
> I guess I can combine both fixes.  What do you think?

Hi Andy,
makes sense to me.

Hugo.


> 
> -- 
> With Best Regards,
> Andy Shevchenko