On Mon, Jan 30, 2017 at 08:03:23AM +0100, Thierry Reding wrote:
> On Mon, Jan 30, 2017 at 07:45:21AM +0100, Greg Kroah-Hartman wrote:
> > On Mon, Jan 30, 2017 at 10:36:29AM +0530, Shailendra Verma wrote:
> > > of_device_get_match_data could return NULL, and so can cause
> > > a NULL pointer dereference later.
> > >
> > > Signed-off-by: Shailendra Verma <shailendra.v@xxxxxxxxxxx>
> > > ---
> > > drivers/usb/host/xhci-tegra.c | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
> > > index a59fafb..890c778 100644
> > > --- a/drivers/usb/host/xhci-tegra.c
> > > +++ b/drivers/usb/host/xhci-tegra.c
> > > @@ -903,6 +903,10 @@ static int tegra_xusb_probe(struct platform_device *pdev)
> > > return -ENOMEM;
> > >
> > > tegra->soc = of_device_get_match_data(&pdev->dev);
> > > + if (!tegra->soc) {
> >
> > How would the driver be loaded and the probe function called if this
> > returns NULL?
> >
> > Is this ever possible?
>
> No, it isn't. I've been NAK'ing this kind of patch for a while now.
> There are two variants of this patch going about:
>
> 1) checking the return value of of_match_device()
> 2) checking the return value of of_device_get_match_data()
>
> The same may also apply to of_match_node(), but I haven't seen that used
> very much lately.
>
> For of_match_device() the problem could technically occur if used in non
> OF setups, because the device could be instantiated by hand in board
> setup code. Tegra has been OF-only for a couple of years now, so there
> is no way this can happen today.
>
> of_device_get_match_data() is somewhat more complicated because it could
> still return NULL if the OF table entry had its .data field set to NULL.
> However in all drivers that I know that would be considered a bug, so
> might as well let things crash at this point to make it immediately
> obvious.
>
> I had once been tempted to write a checkpatch rule for this, but I'm not
> sure it's as easy as just warning if there's a check, because there are
> some legitimate cases, even if they're very rare.
Thanks for the info, patch is now dropped.
Shailendra, please be more careful.
greg k-h
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