Re: [PATCH] usb: u132-hcd: fix potential NULL pointer dereference

[Kangjie Lu]

On 3/19/19 8:56 AM, Greg Kroah-Hartman wrote:
> On Thu, Mar 14, 2019 at 02:27:11AM -0500, Kangjie Lu wrote:
> > In case create_singlethread_workqueue fails, the fix notifies
> > callers the error to avoid potential NULL pointer dereferences.
> >
> > Signed-off-by: Kangjie Lu <kjlu@xxxxxxx>
> > ---
> >   drivers/usb/host/u132-hcd.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/usb/host/u132-hcd.c b/drivers/usb/host/u132-hcd.c
> > index 934584f0a20a..6d5b532b03f8 100644
> > --- a/drivers/usb/host/u132-hcd.c
> > +++ b/drivers/usb/host/u132-hcd.c
> > @@ -3203,6 +3203,8 @@ static int __init u132_hcd_init(void)
> >   		return -ENODEV;
> >   	printk(KERN_INFO "driver %s\n", hcd_name);
> >   	workqueue = create_singlethread_workqueue("u132");
> > +	if (unlikely(!workqueue))
> You only ever use unlikely/likely if you can actually measure the
> difference with and without it.  For stuff like this, it is not needed
> at all, and in fact, the compiler and CPU already know this type of
> thing, so it is going to be faster without it.
>
> And are you sure you properly unwound from anything that was
> created/initialized above these lines?
I didn't see what resources require release in this
case.
Given the existing error paths for usb_disabled() and
platform_driver_register(), returning -ENOMEM looks
like a consistent error handling. Let me know if it
isn't.


> thanks,
>
> greg k-h