"cat /sys/kernel/debug/bcm2835_thermal/regset" causes a NULL pointer
dereference in bcm2835_thermal_debugfs. The driver makes use of the
implementation details of the thermal framework to retrieve a pointer
to its private data from a struct thermal_zone_device, and gets it
wrong - leading to the crash. Instead, store its private data as the
drvdata and retrieve the thermal_zone_device pointer from it.
Fixes: bcb7dd9ef206 ("thermal: bcm2835: add thermal driver for bcm2835 SoC")
Signed-off-by: Phil Elwell <[email protected]>
---
drivers/thermal/broadcom/bcm2835_thermal.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
index 720760c..ba39647 100644
--- a/drivers/thermal/broadcom/bcm2835_thermal.c
+++ b/drivers/thermal/broadcom/bcm2835_thermal.c
@@ -119,8 +119,7 @@ static const struct debugfs_reg32 bcm2835_thermal_regs[] = {
static void bcm2835_thermal_debugfs(struct platform_device *pdev)
{
- struct thermal_zone_device *tz = platform_get_drvdata(pdev);
- struct bcm2835_thermal_data *data = tz->devdata;
+ struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
struct debugfs_regset32 *regset;
data->debugfsdir = debugfs_create_dir("bcm2835_thermal", NULL);
@@ -266,7 +265,7 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
data->tz = tz;
- platform_set_drvdata(pdev, tz);
+ platform_set_drvdata(pdev, data);
/*
* Thermal_zone doesn't enable hwmon as default,
@@ -290,8 +289,8 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
static int bcm2835_thermal_remove(struct platform_device *pdev)
{
- struct thermal_zone_device *tz = platform_get_drvdata(pdev);
- struct bcm2835_thermal_data *data = tz->devdata;
+ struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
+ struct thermal_zone_device *tz = data->tz;
debugfs_remove_recursive(data->debugfsdir);
thermal_zone_of_sensor_unregister(&pdev->dev, tz);
--
2.7.4
On 29/01/2019 10:10, Phil Elwell wrote:
> "cat /sys/kernel/debug/bcm2835_thermal/regset" causes a NULL pointer
> dereference in bcm2835_thermal_debugfs. The driver makes use of the
> implementation details of the thermal framework to retrieve a pointer
> to its private data from a struct thermal_zone_device, and gets it
> wrong - leading to the crash. Instead, store its private data as the
> drvdata and retrieve the thermal_zone_device pointer from it.
>
> Fixes: bcb7dd9ef206 ("thermal: bcm2835: add thermal driver for bcm2835 SoC")
>
> Signed-off-by: Phil Elwell <[email protected]>
Reviewed-by: Daniel Lezcano <[email protected]>
One question: do you really want the thermal driver to be loaded as a
module ? Don't you want to have it operational as soon as possible
instead of waiting the OS to boot and load the kernel module?
If a module format is not needed, then the thermal_zone field won't be
needed anymore because the 'remove' ops can be removed and the need of
the tz field to unregister it disappears.
> ---
> drivers/thermal/broadcom/bcm2835_thermal.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
> index 720760c..ba39647 100644
> --- a/drivers/thermal/broadcom/bcm2835_thermal.c
> +++ b/drivers/thermal/broadcom/bcm2835_thermal.c
> @@ -119,8 +119,7 @@ static const struct debugfs_reg32 bcm2835_thermal_regs[] = {
>
> static void bcm2835_thermal_debugfs(struct platform_device *pdev)
> {
> - struct thermal_zone_device *tz = platform_get_drvdata(pdev);
> - struct bcm2835_thermal_data *data = tz->devdata;
> + struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
> struct debugfs_regset32 *regset;
>
> data->debugfsdir = debugfs_create_dir("bcm2835_thermal", NULL);
> @@ -266,7 +265,7 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
>
> data->tz = tz;
>
> - platform_set_drvdata(pdev, tz);
> + platform_set_drvdata(pdev, data);
>
> /*
> * Thermal_zone doesn't enable hwmon as default,
> @@ -290,8 +289,8 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
>
> static int bcm2835_thermal_remove(struct platform_device *pdev)
> {
> - struct thermal_zone_device *tz = platform_get_drvdata(pdev);
> - struct bcm2835_thermal_data *data = tz->devdata;
> + struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
> + struct thermal_zone_device *tz = data->tz;
>
> debugfs_remove_recursive(data->debugfsdir);
> thermal_zone_of_sensor_unregister(&pdev->dev, tz);
>
--
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Hi Daniel,
On 29/01/2019 09:52, Daniel Lezcano wrote:
> On 29/01/2019 10:10, Phil Elwell wrote:
>> "cat /sys/kernel/debug/bcm2835_thermal/regset" causes a NULL pointer
>> dereference in bcm2835_thermal_debugfs. The driver makes use of the
>> implementation details of the thermal framework to retrieve a pointer
>> to its private data from a struct thermal_zone_device, and gets it
>> wrong - leading to the crash. Instead, store its private data as the
>> drvdata and retrieve the thermal_zone_device pointer from it.
>>
>> Fixes: bcb7dd9ef206 ("thermal: bcm2835: add thermal driver for bcm2835 SoC")
>>
>> Signed-off-by: Phil Elwell <[email protected]>
>
> Reviewed-by: Daniel Lezcano <[email protected]>
>
> One question: do you really want the thermal driver to be loaded as a
> module ? Don't you want to have it operational as soon as possible
> instead of waiting the OS to boot and load the kernel module?
>
> If a module format is not needed, then the thermal_zone field won't be
> needed anymore because the 'remove' ops can be removed and the need of
> the tz field to unregister it disappears.
Thanks for the review. The general approach for Pi drivers has been to make them
tristate to allow minimal kernels to be built - important when the smallest
Pis have 256M - and the delayed startup isn't a problem because the firmware
is running a thermal limiter from before the kernel is loaded. However, this
driver is very small, and I wouldn't object if somebody decided it was better
to make it built-in.
>
>> ---
>> drivers/thermal/broadcom/bcm2835_thermal.c | 9 ++++-----
>> 1 file changed, 4 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
>> index 720760c..ba39647 100644
>> --- a/drivers/thermal/broadcom/bcm2835_thermal.c
>> +++ b/drivers/thermal/broadcom/bcm2835_thermal.c
>> @@ -119,8 +119,7 @@ static const struct debugfs_reg32 bcm2835_thermal_regs[] = {
>>
>> static void bcm2835_thermal_debugfs(struct platform_device *pdev)
>> {
>> - struct thermal_zone_device *tz = platform_get_drvdata(pdev);
>> - struct bcm2835_thermal_data *data = tz->devdata;
>> + struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
>> struct debugfs_regset32 *regset;
>>
>> data->debugfsdir = debugfs_create_dir("bcm2835_thermal", NULL);
>> @@ -266,7 +265,7 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
>>
>> data->tz = tz;
>>
>> - platform_set_drvdata(pdev, tz);
>> + platform_set_drvdata(pdev, data);
>>
>> /*
>> * Thermal_zone doesn't enable hwmon as default,
>> @@ -290,8 +289,8 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
>>
>> static int bcm2835_thermal_remove(struct platform_device *pdev)
>> {
>> - struct thermal_zone_device *tz = platform_get_drvdata(pdev);
>> - struct bcm2835_thermal_data *data = tz->devdata;
>> + struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
>> + struct thermal_zone_device *tz = data->tz;
>>
>> debugfs_remove_recursive(data->debugfsdir);
>> thermal_zone_of_sensor_unregister(&pdev->dev, tz);
>>
>
>
Hi Stefan,
On 29/01/2019 09:44, Stefan Wahren wrote:
> Hi Phil,
>
> Am 29.01.2019 um 10:10 schrieb Phil Elwell:
>> "cat /sys/kernel/debug/bcm2835_thermal/regset" causes a NULL pointer
>> dereference in bcm2835_thermal_debugfs. The driver makes use of the
>> implementation details of the thermal framework to retrieve a pointer
>> to its private data from a struct thermal_zone_device, and gets it
>> wrong - leading to the crash. Instead, store its private data as the
>> drvdata and retrieve the thermal_zone_device pointer from it.
>>
>> Fixes: bcb7dd9ef206 ("thermal: bcm2835: add thermal driver for bcm2835 SoC")
>>
>> Signed-off-by: Phil Elwell <[email protected]>
>
> thanks for this patch.
>
> Could you please resend this patch to the thermal maintainers Zhang Rui and Eduardo Valentin?||||
>
> Regards
> Stefan
>
I blame the get_maintainer script - a "Supporter" sounds less invested and less authoritative
than a "Maintainer".
A resend is imminent.
Phil