| Message ID | 20170530162554.26159-7-johan@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
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 <stable@vger.kernel.org> # 4.9 > Cc: Laxman Dewangan <ldewangan@nvidia.com> > Signed-off-by: Johan Hovold <johan@kernel.org> > --- > 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 = &pdev->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(&pdev->dev, 0, > mtherm, &max77620_thermal_ops); > if (IS_ERR(mtherm->tz_device)) { >
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 <stable@vger.kernel.org> # 4.9 > > Cc: Laxman Dewangan <ldewangan@nvidia.com> > > Signed-off-by: Johan Hovold <johan@kernel.org> > > --- > > 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 = &pdev->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
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 = &pdev->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(&pdev->dev, 0, mtherm, &max77620_thermal_ops); if (IS_ERR(mtherm->tz_device)) {
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 <stable@vger.kernel.org> # 4.9 Cc: Laxman Dewangan <ldewangan@nvidia.com> Signed-off-by: Johan Hovold <johan@kernel.org> --- drivers/thermal/max77620_thermal.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)