On Fri, May 11, 2012 at 12:18:16AM +0300, Alexander Shishkin wrote:
> Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> writes:
>
> > On Thu, May 10, 2012 at 04:25:45PM +0300, Dan Carpenter wrote:
> >> Hello Alexander Shishkin,
> >>
> >> This is a semi-automatic email about new static checker warnings.
> >>
> >> The patch 62bb84ed0e4d: "usb: gadget: ci13xxx: convert to platform
> >> device" from May 8, 2012, leads to the following Smatch complaint:
> >>
> >> drivers/usb/gadget/ci13xxx_pci.c:54 ci13xxx_pci_probe()
> >> warn: variable dereferenced before check 'id' (see line 49)
> >>
> >> drivers/usb/gadget/ci13xxx_pci.c
> >> 48 {
> >> 49 struct ci13xxx_udc_driver *driver = (void *)id->driver_data;
> >> ^^^^^^^^^^^^^^^^
> >> New dereference.
> >>
> >> 50 struct platform_device *plat_ci;
> >> 51 struct resource res[3];
> >> 52 int retval = 0, nres = 2;
> >> 53
> >> 54 if (id == NULL)
> >> ^^^^^^^^^^
> >> Old check. My guess is the check isn't needed.
> >
> > Yes, that is correct, I've now removed that check.
> >
> > What does need to be fixed is the fact that id->driver_data could be
> > null, and bad things can happen later in this function if that is true.
>
> Hmm, I must be missing something here. If id->driver_data is NULL,
> platform_device_add_data() will set plat_ci's platform_data to NULL
> (which it already is anyway) as well, and this is checked for in the
> platform driver's probe. We don't dereference this "driver" pointer in
> this function. What kind of bad things am I still missing here?
You "obviously" do something with that data later right? I thought I
originally found where that was dereferenced, but I can't seem to find
it at the moment, it's in there somewhere...
Oh yeah, in ci_udc_probe() you will error out, and I think somewhere
else as well. Why not just catch that issue here, when it happens, as
it can (think dynamic device ids added through sysfs by a user), so it
should be caught as early as possible.
You are right, it's not "bad things", but it's still sloppy and should
be fixed up.
thanks,
greg k-h
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