UPSTREAM: pwm: Improve args checking in pwm_apply_state()

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>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(cherry picked from commit ef2bf4997f7da6efa8540d9cf726c44bf2b863af)

Change-Id: I7d7515a51b5c3c2a77ae9743b7ed69eedc11d4b4
Signed-off-by: David Wu <david.wu@rock-chips.com>

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 6ec9a0ce9c44753451ac6855f16d659731659a52..869af8448059aa1115ceca08014f2cd658617305 100644 (file)
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -459,7 +459,8 @@ 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 d40c03e5afe3c11ed2736635f3b5f8b325c1df5f..beeecccfe40ecec88f0f72d55e2c5e26c82408b5 100644 (file)
--- 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;