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 <briannor...@chromium.org>
---
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;
--
2.8.0.rc3.226.g39d4020
