linux-kernel - Re: [PATCH] device_core: check null pointer

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Message-ID: <2025111720-sensitize-schnapps-3189@gregkh>
Date: Mon, 17 Nov 2025 07:37:51 -0500
From: Greg KH <gregkh@...uxfoundation.org>
To: Zhengqiao Xia <xiazhengqiao@...qin.corp-partner.google.com>
Cc: rafael@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] device_core: check null pointer

On Mon, Nov 17, 2025 at 10:55:05AM +0800, Zhengqiao Xia wrote:
> Hi Greg,
> 
> Based on my analysis,

Please do not top-post :(

> 
> usb_new_device ->  device_add -> device_private_init
>                                                     ->
> bus_probe_device -> usb_generic_driver_probe  ->
> usb_set_configuration  -> "add each interface"  ->
> device_add(&intf->dev);
> 
> 
>                                     --> if of_node status is disabled
> -> of_device_is_available is false -> not running  device_add ->

Why is of_node related to USB interfaces?

> interface dev->p is null
> usbdev_ioctl -> proc_ioctl -> device_attach -> __device_attach ->
> device_attach ->  if (dev->p->dead)
> 
> Since dev->p has not been created at this time, dev->p is NULL,  So I
> think we should add a check here.
> 
> Here is my current analysis, but there may be some misunderstandings
> or mistakes in it. Could you please help clarify my confusion?

As this code is very old, USB was one of the first subsystems to get
driver core support decades ago, what has changed recently to require
this check?  Have you seen crashes here?  If so, what is the traceback
for them and with what hardware/drivers?

thanks,

greg k-h