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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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?

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

I agree :)

thanks,

greg k-h