Re: [PATCH] pwm: Fill pwm->args before calling pwm_request_from_chip()

From: Thierry Reding
Date: Tue May 17 2016 - 07:04:45 EST


On Tue, May 17, 2016 at 12:35:33PM +0200, Boris Brezillon wrote:
[...]
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index 427142d..3d2eeaa 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -143,10 +143,6 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
> if (args->args[0] >= pc->npwm)
> return ERR_PTR(-EINVAL);
>
> - pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> - if (IS_ERR(pwm))
> - return pwm;
> -
> pwm->args.period = args->args[1];
>
> if (args->args[2] & PWM_POLARITY_INVERTED)
> @@ -154,6 +150,10 @@ of_pwm_xlate_with_flags(struct pwm_chip *pc, const struct of_phandle_args *args)
> else
> pwm->args.polarity = PWM_POLARITY_NORMAL;
>
> + pwm = pwm_request_from_chip(pc, args->args[0], NULL);
> + if (IS_ERR(pwm))
> + return pwm;
> +

Can't do that, because now you're dereferencing an uninitialized
pointer.

> return pwm;
> }
> EXPORT_SYMBOL_GPL(of_pwm_xlate_with_flags);
> @@ -169,12 +169,12 @@ of_pwm_simple_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
> if (args->args[0] >= pc->npwm)
> return ERR_PTR(-EINVAL);
>
> + pwm->args.period = args->args[1];

Same here.

> diff --git a/drivers/pwm/pwm-pxa.c b/drivers/pwm/pwm-pxa.c
> index 58b709f..c33bd42 100644
> --- a/drivers/pwm/pwm-pxa.c
> +++ b/drivers/pwm/pwm-pxa.c
> @@ -156,12 +156,12 @@ pxa_pwm_of_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
> {
> struct pwm_device *pwm;
>
> + pwm->args.period = args->args[0];

And here.

Thierry

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