Messages in this thread | | | Date | Fri, 27 May 2016 18:54:29 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH v2] pwm: improve args checking in pwm_apply_state() |
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On Fri, 27 May 2016 09:45:49 -0700 Brian Norris <briannorris@chromium.org> wrote:
> It seems like in the process of refactoring pwm_config() to utilize the > newly-introduced pwm_apply_state() API, some args/bounds checking was > dropped. > > In particular, I noted that we are now allowing invalid period > selections. e.g.: > > # echo 1 > /sys/class/pwm/pwmchip0/export > # cat /sys/class/pwm/pwmchip0/pwm1/period > 100 > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle > [... driver may or may not reject the value, or trigger some logic bug ...] > > It's better to see: > > # echo 1 > /sys/class/pwm/pwmchip0/export > # cat /sys/class/pwm/pwmchip0/pwm1/period > 100 > # echo 101 > /sys/class/pwm/pwmchip0/pwm1/duty_cycle > -bash: echo: write error: Invalid argument > > This patch reintroduces some bounds checks in both pwm_config() (for its > signed parameters; we don't want to convert negative values into large > unsigned values) and in pwm_apply_state() (which fix the above described > behavior, as well as other potential API misuses). > > Fixes: 5ec803edcb70 ("pwm: Add core infrastructure to allow atomic updates") > Signed-off-by: Brian Norris <briannorris@chromium.org>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Thanks,
Boris
> --- > v2: > * changed subject, as this covers more scope now > * add Fixes tag, as this is a v4.7-rc regression > * add more bounds/args checks in pwm_apply_state() and pwm_config() > > drivers/pwm/core.c | 3 ++- > include/linux/pwm.h | 3 +++ > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c > index dba3843c53b8..ed337a8c34ab 100644 > --- a/drivers/pwm/core.c > +++ b/drivers/pwm/core.c > @@ -457,7 +457,8 @@ int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state) > { > int err; > > - if (!pwm) > + if (!pwm || !state || !state->period || > + state->duty_cycle > state->period) > return -EINVAL; > > if (!memcmp(state, &pwm->state, sizeof(*state))) > diff --git a/include/linux/pwm.h b/include/linux/pwm.h > index 17018f3c066e..908b67c847cd 100644 > --- a/include/linux/pwm.h > +++ b/include/linux/pwm.h > @@ -235,6 +235,9 @@ static inline int pwm_config(struct pwm_device *pwm, int duty_ns, > if (!pwm) > return -EINVAL; > > + if (duty_ns < 0 || period_ns < 0) > + return -EINVAL; > + > pwm_get_state(pwm, &state); > if (state.duty_cycle == duty_ns && state.period == period_ns) > return 0;
-- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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