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[PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0

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  [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0 Wolfram Sang <wsa@the-dreams.de> - 2016-03-02 23:40 +0100
    Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid  division by 0 Joachim Eastwood <manabian@gmail.com> - 2016-03-02 23:50 +0100
      Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid  division by 0 Wolfram Sang <wsa@the-dreams.de> - 2016-03-03 00:00 +0100

#1348574 — [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

The clk API may return 0 on clk_get_rate, so we should check the result before
using it as a divisor.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---

Should go individually via subsystem tree.

 drivers/pwm/pwm-lpc18xx-sct.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
index 9163085101bc94..6487962c355c03 100644
--- a/drivers/pwm/pwm-lpc18xx-sct.c
+++ b/drivers/pwm/pwm-lpc18xx-sct.c
@@ -360,6 +360,8 @@ static int lpc18xx_pwm_probe(struct platform_device *pdev)
 	}
 
 	lpc18xx_pwm->clk_rate = clk_get_rate(lpc18xx_pwm->pwm_clk);
+	if (!lpc18xx_pwm->clk_rate)
+		return -EINVAL;
 
 	mutex_init(&lpc18xx_pwm->res_lock);
 	mutex_init(&lpc18xx_pwm->period_lock);
-- 
2.7.0

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#1348582 — Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0

Hi Wolfram,

On 2 March 2016 at 23:33, Wolfram Sang <wsa@the-dreams.de> wrote:
> From: Wolfram Sang <wsa+renesas@sang-engineering.com>
>
> The clk API may return 0 on clk_get_rate, so we should check the result before
> using it as a divisor.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> ---
>
> Should go individually via subsystem tree.
>
>  drivers/pwm/pwm-lpc18xx-sct.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
> index 9163085101bc94..6487962c355c03 100644
> --- a/drivers/pwm/pwm-lpc18xx-sct.c
> +++ b/drivers/pwm/pwm-lpc18xx-sct.c
> @@ -360,6 +360,8 @@ static int lpc18xx_pwm_probe(struct platform_device *pdev)
>         }
>
>         lpc18xx_pwm->clk_rate = clk_get_rate(lpc18xx_pwm->pwm_clk);
> +       if (!lpc18xx_pwm->clk_rate)
> +               return -EINVAL;

This needs to be:
if (!lpc18xx_pwm->clk_rate) {
    ret = -EINVAL;
    goto disable_pwmclk;
}

I would also prefer an explicit check against 0 here. ie.:
'lpc18xx_pwm->clk_rate == 0'
A dev_err() message would also be nice to have.


regards,
Joachim Eastwood

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#1348586 — Re: [PATCH 4/6] pwm: pwm-lpc18xx-sct: test clock rate to avoid division by 0

[Multipart message — attachments visible in raw view] — view raw

On Wed, Mar 02, 2016 at 11:44:02PM +0100, Joachim Eastwood wrote:
> Hi Wolfram,
> 
> On 2 March 2016 at 23:33, Wolfram Sang <wsa@the-dreams.de> wrote:
> > From: Wolfram Sang <wsa+renesas@sang-engineering.com>
> >
> > The clk API may return 0 on clk_get_rate, so we should check the result before
> > using it as a divisor.
> >
> > Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
> > ---
> >
> > Should go individually via subsystem tree.
> >
> >  drivers/pwm/pwm-lpc18xx-sct.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
> > index 9163085101bc94..6487962c355c03 100644
> > --- a/drivers/pwm/pwm-lpc18xx-sct.c
> > +++ b/drivers/pwm/pwm-lpc18xx-sct.c
> > @@ -360,6 +360,8 @@ static int lpc18xx_pwm_probe(struct platform_device *pdev)
> >         }
> >
> >         lpc18xx_pwm->clk_rate = clk_get_rate(lpc18xx_pwm->pwm_clk);
> > +       if (!lpc18xx_pwm->clk_rate)
> > +               return -EINVAL;
> 
> This needs to be:
> if (!lpc18xx_pwm->clk_rate) {
>     ret = -EINVAL;
>     goto disable_pwmclk;
> }

Yes, that slipped through. Thanks!

> I would also prefer an explicit check against 0 here. ie.:

Well, I like the reading "if not rate then error"

Will send V2 now...

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