Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create_dev

[Pavel Skripkin]

Hi Dongliang,

On 1/21/22 08:58, Dongliang Mu wrote:
[...]>> BTW, as you mentioned, dev->next_siblings is used in struct
> > peak_usb_adapter::dev_free() (i.e., pcan_usb_fd_free or
> > pcan_usb_pro_free), how about the following path?
> >
> > peak_usb_probe
> > -> peak_usb_create_dev (goto adap_dev_free;)
> >    -> dev->adapter->dev_free()
> >       -> pcan_usb_fd_free or pcan_usb_pro_free (This function uses
> > next_siblings as condition elements)
> >
> > static void pcan_usb_fd_free(struct peak_usb_device *dev)
> > {
> >         /* last device: can free shared objects now */
> >         if (!dev->prev_siblings && !dev->next_siblings) {
> >                 struct pcan_usb_fd_device *pdev =
> >                         container_of(dev, struct pcan_usb_fd_device, dev);
> >
> >                 /* free commands buffer */
> >                 kfree(pdev->cmd_buffer_addr);
> >
> >                 /* free usb interface object */
> >                 kfree(pdev->usb_if);
> >         }
> > }
> >
> > If next_siblings is not NULL, will it lead to the missing free of
> > cmd_buffer_addr and usb_if?
>
> The answer is No. Forget my silly thought.

Yeah, it seems like (at least based on code), that this dangling pointer 
is not dangerous, since nothing accesses it. And next_siblings 
_guaranteed_ to be NULL, since dev->next_siblings is set NULL in 
disconnect()




With regards,
Pavel Skripkin