]> git.karo-electronics.de Git - linux-beck.git/commit
pwm: Improve args checking in pwm_apply_state()
authorBrian Norris <briannorris@chromium.org>
Fri, 27 May 2016 16:45:49 +0000 (09:45 -0700)
committerThierry Reding <thierry.reding@gmail.com>
Fri, 10 Jun 2016 12:21:00 +0000 (14:21 +0200)
commitef2bf4997f7da6efa8540d9cf726c44bf2b863af
treea90229605b8dfeedd6bb010dffee63e3df74b417
parent1a695a905c18548062509178b98bc91e67510864
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>
drivers/pwm/core.c
include/linux/pwm.h