Re: [REGRESSION 5.19] NULL dereference by ucsi_acpi driver

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Aug 19, 2022 at 06:32:43PM +0200, Takashi Iwai wrote:
> Hi,
> 
> we've got multiple reports about 5.19 kernel starting crashing after
> some time, and this turned out to be triggered by ucsi_acpi driver.
> The details are found in:
>   https://bugzilla.suse.com/show_bug.cgi?id=1202386
> 
> The culprit seems to be the commit 87d0e2f41b8c
>     usb: typec: ucsi: add a common function ucsi_unregister_connectors()

Adding Heikki to the thread...

>     
> This commit looks as if it were a harmless cleanup, but this failed in
> a subtle way.  Namely, in the error scenario, the driver gets an error
> at ucsi_register_altmodes(), and goes to the error handling to release
> the resources.  Through this refactoring, the release part was unified
> to a funciton ucsi_unregister_connectors().  And there, it has a NULL
> check of con->wq, and it bails out the loop if it's NULL. 
> Meanwhile, ucsi_register_port() itself still calls destroy_workqueue()
> and clear con->wq at its error path.  This ended up in the leftover
> power supply device with the uninitialized / cleared device.
> 
> It was confirmed that the problem could be avoided by a simple
> revert.

I'll be glad to revert this now, unless Heikki thinks:

> 
> I guess another fix could be removing the part clearing con->wq, i.e.
> 
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -1192,11 +1192,6 @@ static int ucsi_register_port(struct ucsi *ucsi, int index)
>  out_unlock:
>  	mutex_unlock(&con->lock);
>  
> -	if (ret && con->wq) {
> -		destroy_workqueue(con->wq);
> -		con->wq = NULL;
> -	}
> -
>  	return ret;
>  }
>  
> 
> ... but it's totally untested and I'm not entirely sure whether it's
> better.

that is any better?

thanks,

greg k-h