Re: [PATCH 1/3] mmc: sdhci-s3c: fix possible NULL pointer dereference when probed via platform

[Sylwester Nawrocki]

On 14.04.2021 17:25, Krzysztof Kozlowski wrote:
> On 14/04/2021 17:12, Krzysztof Kozlowski wrote:
> > The driver can be matched by legacy platform way or OF-device matching.
> > In the first case, of_match_node() can return NULL, which immediately
> > would be dereferenced to get the match data.
> >
> > Addresses-Coverity: Dereference null return value
> > Fixes: cd1b00eb24b0 ("mmc: sdhci-s3c: Add device tree support")
> > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxx>

> > -#ifdef CONFIG_OF
> > -static const struct of_device_id sdhci_s3c_dt_match[];
> > -#endif
> > -
> >   static inline struct sdhci_s3c_drv_data *sdhci_s3c_get_driver_data(
> >   			struct platform_device *pdev)
> >   {
> >   #ifdef CONFIG_OF
> > -	if (pdev->dev.of_node) {
> > -		const struct of_device_id *match;
> > -		match = of_match_node(sdhci_s3c_dt_match, pdev->dev.of_node);
>
> Now I have second thoughts whether NULL pointer can actually happen.  If
> device is matched via platform/board files, maybe the pdev->dev.of_node
> will be NULL thus skipping this branch?
>
> Could there be a case where device is matched via platform_device_id()
> (which has different name than compatible!) and (pdev->dev.of_node) is
> still assigned? Maybe in case of out of tree DTS?

That seems unlikely, the platform device would need to be initialized
via board file and then its of_node assigned somehow. It doesn't make
much sense to me. We either use board file or dtb to instantiate devices.

> Anyway, the patch makes the code simpler/smaller, so I still think it is
> reasonable. Just the severity of issue is questionable...

Yes, the patch looks good. Similar cleanups are already done in most of
the s3c/s5p/exynos drivers.

--
Thanks,
Sylwester