Re: [PATCH 6/7] thermal: max77620: fix device-node reference imbalance
On Tue, May 30, 2017 at 03:59:10PM -0700, Tyrel Datwyler wrote:
> On 05/30/2017 09:25 AM, Johan Hovold wrote:
> > The thermal child device reuses the parent MFD-device device-tree node
> > when registering a thermal zone, but did not take a reference to the
> > node.
> >
> > This leads to a reference imbalance, and potential use-after-free, when
> > the node reference is dropped by the platform-bus device destructor
> > (once for the child and later again for the parent).
> >
> > Fix this by dropping any reference already held to a device-tree node
> > and getting a reference to the parent's node which will be balanced on
> > reprobe or on platform-device release, whichever comes first.
> >
> > Note that simply clearing the of_node pointer on probe errors and on
> > driver unbind would not allow the use of device-managed resources as
> > specifically thermal_zone_of_sensor_unregister() claims that a valid
> > device-tree node pointer is needed during deregistration (even if it
> > currently does not seem to use it).
> >
> > Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
> > junction temp")
> > Cc: stable # 4.9
> > Cc: Laxman Dewangan
> > Signed-off-by: Johan Hovold
> > ---
> > drivers/thermal/max77620_thermal.c | 10 --
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/thermal/max77620_thermal.c
> > b/drivers/thermal/max77620_thermal.c
> > index e9a1fe342760..71d35f3c9215 100644
> > --- a/drivers/thermal/max77620_thermal.c
> > +++ b/drivers/thermal/max77620_thermal.c
> > @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct
> > platform_device *pdev)
> > return -EINVAL;
> > }
> >
> > - pdev->dev.of_node = pdev->dev.parent->of_node;
> > -
> > mtherm->dev = >dev;
> > mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
> > if (!mtherm->rmap) {
> > @@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct
> > platform_device *pdev)
> > return -ENODEV;
> > }
> >
> > + /*
> > +* Drop any current reference to a device-tree node and get a
> > +* reference to the parent's node which will be balanced on reprobe or
> > +* on platform-device release.
> > +*/
> > + of_node_put(pdev->dev.of_node);
> > + pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
> > +
>
> This seems like needless churn. Can't this just be squashed into patch
> #7?
As I just replied to Eduardo, I'm fixing two separate issues here of
which this one might qualify for stable while the other (7/7) does not.
Thanks,
Johan
Re: [PATCH 6/7] thermal: max77620: fix device-node reference imbalance
On Tue, May 30, 2017 at 03:59:10PM -0700, Tyrel Datwyler wrote:
> On 05/30/2017 09:25 AM, Johan Hovold wrote:
> > The thermal child device reuses the parent MFD-device device-tree node
> > when registering a thermal zone, but did not take a reference to the
> > node.
> >
> > This leads to a reference imbalance, and potential use-after-free, when
> > the node reference is dropped by the platform-bus device destructor
> > (once for the child and later again for the parent).
> >
> > Fix this by dropping any reference already held to a device-tree node
> > and getting a reference to the parent's node which will be balanced on
> > reprobe or on platform-device release, whichever comes first.
> >
> > Note that simply clearing the of_node pointer on probe errors and on
> > driver unbind would not allow the use of device-managed resources as
> > specifically thermal_zone_of_sensor_unregister() claims that a valid
> > device-tree node pointer is needed during deregistration (even if it
> > currently does not seem to use it).
> >
> > Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
> > junction temp")
> > Cc: stable # 4.9
> > Cc: Laxman Dewangan
> > Signed-off-by: Johan Hovold
> > ---
> > drivers/thermal/max77620_thermal.c | 10 --
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/thermal/max77620_thermal.c
> > b/drivers/thermal/max77620_thermal.c
> > index e9a1fe342760..71d35f3c9215 100644
> > --- a/drivers/thermal/max77620_thermal.c
> > +++ b/drivers/thermal/max77620_thermal.c
> > @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct
> > platform_device *pdev)
> > return -EINVAL;
> > }
> >
> > - pdev->dev.of_node = pdev->dev.parent->of_node;
> > -
> > mtherm->dev = >dev;
> > mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
> > if (!mtherm->rmap) {
> > @@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct
> > platform_device *pdev)
> > return -ENODEV;
> > }
> >
> > + /*
> > +* Drop any current reference to a device-tree node and get a
> > +* reference to the parent's node which will be balanced on reprobe or
> > +* on platform-device release.
> > +*/
> > + of_node_put(pdev->dev.of_node);
> > + pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
> > +
>
> This seems like needless churn. Can't this just be squashed into patch
> #7?
As I just replied to Eduardo, I'm fixing two separate issues here of
which this one might qualify for stable while the other (7/7) does not.
Thanks,
Johan
Re: [PATCH 6/7] thermal: max77620: fix device-node reference imbalance
On 05/30/2017 09:25 AM, Johan Hovold wrote:
> The thermal child device reuses the parent MFD-device device-tree node
> when registering a thermal zone, but did not take a reference to the
> node.
>
> This leads to a reference imbalance, and potential use-after-free, when
> the node reference is dropped by the platform-bus device destructor
> (once for the child and later again for the parent).
>
> Fix this by dropping any reference already held to a device-tree node
> and getting a reference to the parent's node which will be balanced on
> reprobe or on platform-device release, whichever comes first.
>
> Note that simply clearing the of_node pointer on probe errors and on
> driver unbind would not allow the use of device-managed resources as
> specifically thermal_zone_of_sensor_unregister() claims that a valid
> device-tree node pointer is needed during deregistration (even if it
> currently does not seem to use it).
>
> Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
> junction temp")
> Cc: stable # 4.9
> Cc: Laxman Dewangan
> Signed-off-by: Johan Hovold
> ---
> drivers/thermal/max77620_thermal.c | 10 --
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/max77620_thermal.c
> b/drivers/thermal/max77620_thermal.c
> index e9a1fe342760..71d35f3c9215 100644
> --- a/drivers/thermal/max77620_thermal.c
> +++ b/drivers/thermal/max77620_thermal.c
> @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct platform_device
> *pdev)
> return -EINVAL;
> }
>
> - pdev->dev.of_node = pdev->dev.parent->of_node;
> -
> mtherm->dev = >dev;
> mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
> if (!mtherm->rmap) {
> @@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct platform_device
> *pdev)
> return -ENODEV;
> }
>
> + /*
> + * Drop any current reference to a device-tree node and get a
> + * reference to the parent's node which will be balanced on reprobe or
> + * on platform-device release.
> + */
> + of_node_put(pdev->dev.of_node);
> + pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
> +
This seems like needless churn. Can't this just be squashed into patch #7?
-Tyrel
> mtherm->tz_device = devm_thermal_zone_of_sensor_register(>dev, 0,
> mtherm, _thermal_ops);
> if (IS_ERR(mtherm->tz_device)) {
>
Re: [PATCH 6/7] thermal: max77620: fix device-node reference imbalance
On 05/30/2017 09:25 AM, Johan Hovold wrote:
> The thermal child device reuses the parent MFD-device device-tree node
> when registering a thermal zone, but did not take a reference to the
> node.
>
> This leads to a reference imbalance, and potential use-after-free, when
> the node reference is dropped by the platform-bus device destructor
> (once for the child and later again for the parent).
>
> Fix this by dropping any reference already held to a device-tree node
> and getting a reference to the parent's node which will be balanced on
> reprobe or on platform-device release, whichever comes first.
>
> Note that simply clearing the of_node pointer on probe errors and on
> driver unbind would not allow the use of device-managed resources as
> specifically thermal_zone_of_sensor_unregister() claims that a valid
> device-tree node pointer is needed during deregistration (even if it
> currently does not seem to use it).
>
> Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
> junction temp")
> Cc: stable # 4.9
> Cc: Laxman Dewangan
> Signed-off-by: Johan Hovold
> ---
> drivers/thermal/max77620_thermal.c | 10 --
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/max77620_thermal.c
> b/drivers/thermal/max77620_thermal.c
> index e9a1fe342760..71d35f3c9215 100644
> --- a/drivers/thermal/max77620_thermal.c
> +++ b/drivers/thermal/max77620_thermal.c
> @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct platform_device
> *pdev)
> return -EINVAL;
> }
>
> - pdev->dev.of_node = pdev->dev.parent->of_node;
> -
> mtherm->dev = >dev;
> mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
> if (!mtherm->rmap) {
> @@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct platform_device
> *pdev)
> return -ENODEV;
> }
>
> + /*
> + * Drop any current reference to a device-tree node and get a
> + * reference to the parent's node which will be balanced on reprobe or
> + * on platform-device release.
> + */
> + of_node_put(pdev->dev.of_node);
> + pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
> +
This seems like needless churn. Can't this just be squashed into patch #7?
-Tyrel
> mtherm->tz_device = devm_thermal_zone_of_sensor_register(>dev, 0,
> mtherm, _thermal_ops);
> if (IS_ERR(mtherm->tz_device)) {
>
[PATCH 6/7] thermal: max77620: fix device-node reference imbalance
The thermal child device reuses the parent MFD-device device-tree node
when registering a thermal zone, but did not take a reference to the
node.
This leads to a reference imbalance, and potential use-after-free, when
the node reference is dropped by the platform-bus device destructor
(once for the child and later again for the parent).
Fix this by dropping any reference already held to a device-tree node
and getting a reference to the parent's node which will be balanced on
reprobe or on platform-device release, whichever comes first.
Note that simply clearing the of_node pointer on probe errors and on
driver unbind would not allow the use of device-managed resources as
specifically thermal_zone_of_sensor_unregister() claims that a valid
device-tree node pointer is needed during deregistration (even if it
currently does not seem to use it).
Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
junction temp")
Cc: stable # 4.9
Cc: Laxman Dewangan
Signed-off-by: Johan Hovold
---
drivers/thermal/max77620_thermal.c | 10 --
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/thermal/max77620_thermal.c
b/drivers/thermal/max77620_thermal.c
index e9a1fe342760..71d35f3c9215 100644
--- a/drivers/thermal/max77620_thermal.c
+++ b/drivers/thermal/max77620_thermal.c
@@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct platform_device
*pdev)
return -EINVAL;
}
- pdev->dev.of_node = pdev->dev.parent->of_node;
-
mtherm->dev = >dev;
mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
if (!mtherm->rmap) {
@@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct platform_device
*pdev)
return -ENODEV;
}
+ /*
+* Drop any current reference to a device-tree node and get a
+* reference to the parent's node which will be balanced on reprobe or
+* on platform-device release.
+*/
+ of_node_put(pdev->dev.of_node);
+ pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
+
mtherm->tz_device = devm_thermal_zone_of_sensor_register(>dev, 0,
mtherm, _thermal_ops);
if (IS_ERR(mtherm->tz_device)) {
--
2.13.0
[PATCH 6/7] thermal: max77620: fix device-node reference imbalance
The thermal child device reuses the parent MFD-device device-tree node
when registering a thermal zone, but did not take a reference to the
node.
This leads to a reference imbalance, and potential use-after-free, when
the node reference is dropped by the platform-bus device destructor
(once for the child and later again for the parent).
Fix this by dropping any reference already held to a device-tree node
and getting a reference to the parent's node which will be balanced on
reprobe or on platform-device release, whichever comes first.
Note that simply clearing the of_node pointer on probe errors and on
driver unbind would not allow the use of device-managed resources as
specifically thermal_zone_of_sensor_unregister() claims that a valid
device-tree node pointer is needed during deregistration (even if it
currently does not seem to use it).
Fixes: ec4664b3fd6d ("thermal: max77620: Add thermal driver for reporting
junction temp")
Cc: stable # 4.9
Cc: Laxman Dewangan
Signed-off-by: Johan Hovold
---
drivers/thermal/max77620_thermal.c | 10 --
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/thermal/max77620_thermal.c
b/drivers/thermal/max77620_thermal.c
index e9a1fe342760..71d35f3c9215 100644
--- a/drivers/thermal/max77620_thermal.c
+++ b/drivers/thermal/max77620_thermal.c
@@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct platform_device
*pdev)
return -EINVAL;
}
- pdev->dev.of_node = pdev->dev.parent->of_node;
-
mtherm->dev = >dev;
mtherm->rmap = dev_get_regmap(pdev->dev.parent, NULL);
if (!mtherm->rmap) {
@@ -113,6 +111,14 @@ static int max77620_thermal_probe(struct platform_device
*pdev)
return -ENODEV;
}
+ /*
+* Drop any current reference to a device-tree node and get a
+* reference to the parent's node which will be balanced on reprobe or
+* on platform-device release.
+*/
+ of_node_put(pdev->dev.of_node);
+ pdev->dev.of_node = of_node_get(pdev->dev.parent->of_node);
+
mtherm->tz_device = devm_thermal_zone_of_sensor_register(>dev, 0,
mtherm, _thermal_ops);
if (IS_ERR(mtherm->tz_device)) {
--
2.13.0
