Re: [PATCH 2/2] usb: musb: Fix a possible null-pointer dereference in musb_handle_intr_connect()

[Jia-Ju Bai <baijiaju1990@gmail.com>]

On 2019/12/11 17:20, Greg Kroah-Hartman wrote:
> On Wed, Dec 11, 2019 at 05:10:17PM +0800, Jia-Ju Bai wrote:
>>
>> On 2019/12/11 16:09, Greg Kroah-Hartman wrote:
>>> On Tue, Dec 10, 2019 at 10:54:54AM -0600, Bin Liu wrote:
>>>> From: Jia-Ju Bai <baijiaju1990@gmail.com>
>>>>
>>>> In musb_handle_intr_connect(), there is an if statement on line 783 to
>>>> check whether musb->hcd is NULL:
>>>>       if (musb->hcd)
>>>>
>>>> When musb->hcd is NULL, it is used on line 797:
>>>>       musb_host_poke_root_hub(musb);
>>>>           if (musb->hcd->status_urb)
>>>>
>>>> Thus, a possible null-pointer dereference may occur.
>>> Maybe, if musb->hcd really ever could be NULL.
>>>
>>> In looking at the code, I don't see where that could happen, do you?
>>> Why is that check there in the first place?
>>>
>>> What sets musb->hcd to NULL in the first place?
>> In fact, my static analysis tool identifies an if check about musb->hcd, so
>> it infers that musb->hcd could be NULL here.
>> But it does not try to find any explicit place that set musb->hcd to NULL.
> Can it do that?

Not yet...

>
>> If musb->hcd is never NULL here, we can just delete the related if check.
> I agree :)

Okay, I will send a new patch that delete the if check.


Best wishes,
Jia-Ju Bai