Re: [PATCH] drivers/xillybus: fix deadlock upon cleanup_dev

[Eli Billauer]

Hello,

I should have sent a response to this syzbot alert, indicating that 
there is already ongoing work to fix this issue:

https://lore.kernel.org/lkml/20240801121126.60183-1-eli.billauer@xxxxxxxxx/

My apologies for not doing that.

On 13/08/2024 7:04, Sabyrzhan Tasbolatov wrote:
> syzbot found an issue [1] when cleanup_dev() is called twice,
> causing deadlock.

How is cleanup_dev() called twice? I only see it once in the stack trace.

 It is called in xillyusb_probe()
> in the end of wakeup_all():
>
> 	INIT_WORK(&xdev->wakeup_workitem, wakeup_all);

INIT_WORK merely initializes the work item, it doesn't cause its execution.

> @@ -2174,7 +2175,6 @@ static int xillyusb_probe(struct usb_interface *interface,
>   
>   fail:
>   	usb_set_intfdata(interface, NULL);
> -	kref_put(&xdev->kref, cleanup_dev);
>   	return rc;
>   }
>   

This edit causes a memory leak, because the reference count needs to be 
decremented in other failure scenarios.

Thanks,
   Eli