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:

quoted

There are two bugs:

You should break this up into two separate patches, one for each bug.

quoted

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.

quoted

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