Re: [PATCH] HID: elo: Fix refcount leak in elo_probe()

[Greg KH <greg@kroah.com>]

On Thu, Feb 17, 2022 at 10:25:02AM -0500, Alan Stern wrote:
> On Thu, Feb 17, 2022 at 11:04:59AM +0300, Dan Carpenter wrote:
> > Salah sent a bunch of these.  The reasoning was explained in this email.
> > 
> > https://www.spinics.net/lists/kernel/msg4026672.html
> > 
> > When he resent the patch, Greg said that taking the reference wasn't
> > needed so the patch wasn't applied.  (Also it had the same reference
> > leak so that's a second reason it wasn't applied).
> 
> Indeed, the kerneldoc for usb_get_intf() does say that each reference 
> held by a driver must be refcounted.  And there's nothing wrong with 
> doing that, _provided_ you do it correctly.
> 
> But if you know the extra refcount will never be needed (because the 
> reference will be dropped before the usb_interface in question is 
> removed), fiddling with the reference count is unnecessary.  I guess 
> whether or not to do it could be considered a matter of taste.
> 
> On the other hand, it wouldn't hurt to update the kerneldoc for 
> usb_get_intf() (and usb_get_dev() also).  We could point out that if a 
> driver does not access the usb_interface structure after its disconnect 
> routine returns, incrementing the refcount isn't mandatory.

That would be good to add to prevent this type of confusion in the
future.

thanks,

greg k-h