[PATCH 6.1 0866/1146] pwm: sifive: Call pwm_sifive_update_clock() while mutex is held

Greg Kroah-Hartman
2022-12-28T16:43:57Z

From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

[ Upstream commit 45558b3abb87eeb2cedb8a59cb2699c120b5102a ]

As was documented in commit 0f02f491b786 ("pwm: sifive: Reduce time the
controller lock is held") a caller of pwm_sifive_update_clock() must
hold the mutex. So fix pwm_sifive_clock_notifier() to grab the lock.

While this necessity was only documented later, the race exists since
the driver was introduced.

Fixes: 9e37a53eb051 ("pwm: sifive: Add a driver for SiFive SoC PWM")
Reported-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Reviewed-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/r/20221018061656.1428111-1-u.kleine-koenig@pengutronix.de
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/pwm/pwm-sifive.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index 2d4fa5e5fdd4..bb7239313401 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -204,8 +204,11 @@ static int pwm_sifive_clock_notifier(struct notifier_block *nb,
struct pwm_sifive_ddata *ddata =
container_of(nb, struct pwm_sifive_ddata, notifier);

- if (event == POST_RATE_CHANGE)
+ if (event == POST_RATE_CHANGE) {
+ mutex_lock(&ddata->lock);
pwm_sifive_update_clock(ddata, ndata->new_rate);
+ mutex_unlock(&ddata->lock);
+ }

return NOTIFY_OK;
}
--
2.35.1