2022-06-14 11:26:59

by Christian Marangi

Subject: [PATCH v3 3/5] PM / devfreq: Fix kernel panic with cpu based scaling to passive gov

The cpufreq passive register notifier can PROBE_DEFER and the devfreq
struct is freed and then reallocaed on probe retry.
The current logic assume that the code can't PROBE_DEFER so the devfreq
struct in the this variable in devfreq_passive_data is assumed to be
(if already set) always correct.
This cause kernel panic as the code try to access the wrong address.
To correctly handle this, update the this variable in
devfreq_passive_data to the devfreq reallocated struct.

Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
Signed-off-by: Christian 'Ansuel' Marangi <[email protected]>
---
drivers/devfreq/governor_passive.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
index 3c3322adea03..be8aa6830413 100644
--- a/drivers/devfreq/governor_passive.c
+++ b/drivers/devfreq/governor_passive.c
@@ -395,8 +395,7 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
if (!p_data)
return -EINVAL;

- if (!p_data->this)
- p_data->this = devfreq;
+ p_data->this = devfreq;

switch (event) {
case DEVFREQ_GOV_START:
--
2.36.1

2022-06-14 23:34:09

by Chanwoo Choi

Subject: Re: [PATCH v3 3/5] PM / devfreq: Fix kernel panic with cpu based scaling to passive gov

On 22. 6. 14. 20:06, Christian 'Ansuel' Marangi wrote:
> The cpufreq passive register notifier can PROBE_DEFER and the devfreq
> struct is freed and then reallocaed on probe retry.
> The current logic assume that the code can't PROBE_DEFER so the devfreq
> struct in the this variable in devfreq_passive_data is assumed to be
> (if already set) always correct.
> This cause kernel panic as the code try to access the wrong address.
> To correctly handle this, update the this variable in
> devfreq_passive_data to the devfreq reallocated struct.
>
> Fixes: a03dacb0316f ("PM / devfreq: Add cpu based scaling support to passive governor")
> Signed-off-by: Christian 'Ansuel' Marangi <[email protected]>
> ---
> drivers/devfreq/governor_passive.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 3c3322adea03..be8aa6830413 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -395,8 +395,7 @@ static int devfreq_passive_event_handler(struct devfreq *devfreq,
> if (!p_data)
> return -EINVAL;
>
> - if (!p_data->this)
> - p_data->this = devfreq;
> + p_data->this = devfreq;
>
> switch (event) {
> case DEVFREQ_GOV_START:

Applied it to devfreq-fixes. Thanks.

--
Best Regards,
Samsung Electronics
Chanwoo Choi