Re: [PATCH] usb: gadget: use after free in dev_config

[Hangyu Hua]

Thank for your suggesions. I will break this up into two separate 
patches later. And i think it's necessary to clear up dev->config and
dev->hs_config and dev->dev. For example, dev->hs_config is used in
ep0_read() which may lead a UAF.

Thanks.

On 2021/12/30 上午5:11, Alan Stern wrote:
> On Tue, Dec 28, 2021 at 05:21:26PM +0800, Hangyu Hua wrote:
> > There are two bugs:
>
> You should break this up into two separate patches, one for each bug.
>
> > dev->buf does not need to be released if it already exists before
> > executing dev_config.
>
> That's right.  The call to dev_config should fail without changing any
> of the stored values.
>
> > dev->config and dev->hs_config and dev->dev need to be cleaned if
> > dev_config fails to avoid UAF.
>
> Do they really need to be cleared?  I think if dev_config fails then
> those pointers never get used, so it doesn't matter what they contain.
>
> Of course, clearing them doesn't hurt, but it would be best to clear
> all of them in the "fail:" part of the routine.  And then you would
> want to change the pathway where usb_gadget_probe_driver fails, to make
> it go to "fail:" also.
>
> Alan Stern