Re: [PATCH v1 1/5] pwm: mediatek: add a property "mediatek,num-pwms"

Ryder Lee
2019-01-18T09:47:33Z

On Fri, 2019-01-18 at 09:05 +0100, Uwe Kleine-König wrote:
> Hello,
>
> just realized another issue while looking up a driver detail ...
>
> On Fri, Jan 18, 2019 at 11:24:41AM +0800, Ryder Lee wrote:
> > This adds a property "mediatek,num-pwms" to avoid having an endless
> > list of compatibles with no differences for the same driver.
> >
> > Thus, the driver should have backwards compatibility to older DTs.
> >
> > Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
> > ---
> > Changes since v1: add some checks for backwards compatibility.
> > ---
> > drivers/pwm/pwm-mediatek.c | 27 ++++++++++++++++++---------
> > 1 file changed, 18 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
> > index eb6674c..81b7e5e 100644
> > --- a/drivers/pwm/pwm-mediatek.c
> > +++ b/drivers/pwm/pwm-mediatek.c
> > @@ -55,7 +55,7 @@ enum {
> > };
> >
> > struct mtk_pwm_platform_data {
> > - unsigned int num_pwms;
> > + unsigned int num_pwms; /* it should not be used in the future SoCs */
> > bool pwm45_fixup;
> > bool has_clks;
> > };
> > @@ -226,27 +226,36 @@ static void mtk_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> >
> > static int mtk_pwm_probe(struct platform_device *pdev)
> > {
> > - const struct mtk_pwm_platform_data *data;
> > + struct device_node *np = pdev->dev.of_node;
> > struct mtk_pwm_chip *pc;
> > struct resource *res;
> > - unsigned int i;
> > + unsigned int i, num_pwms;
> > int ret;
> >
> > pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
> > if (!pc)
> > return -ENOMEM;
> >
> > - data = of_device_get_match_data(&pdev->dev);
> > - if (data == NULL)
> > - return -EINVAL;
> > - pc->soc = data;
> > + pc->soc = of_device_get_match_data(&pdev->dev);
> >
> > res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > pc->regs = devm_ioremap_resource(&pdev->dev, res);
> > if (IS_ERR(pc->regs))
> > return PTR_ERR(pc->regs);
> >
> > - for (i = 0; i < data->num_pwms + 2 && pc->soc->has_clks; i++) {
> > + /* Check if we have set 'num-pwms' in DTs. */
> > + ret = of_property_read_u32(np, "mediatek,num-pwms", &num_pwms);
> > + if (ret < 0) {
> > + /* If no, fallback to use SoC data for backwards compatibility. */
> > + if (pc->soc->num_pwms) {
> > + num_pwms = pc->soc->num_pwms;
> > + } else {
> > + dev_err(&pdev->dev, "failed to get pwm number: %d\n", ret);
> > + return ret;
> > + }
> > + }
> > +
> > + for (i = 0; i < num_pwms + 2 && pc->soc->has_clks; i++) {
> > pc->clks[i] = devm_clk_get(&pdev->dev, mtk_pwm_clk_name[i]);
>
> If a dt contains
>
> mediatek,num-pwms = <17>;
>
> you're accessing pc->clks[18] which is an out-of-bounds access, so
> better check the limit or allocate the clks array dynamically.
>

Thanks for the reminder. I will fix it in v2.

Ryder