Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 005/125] thermal: max77620: fix device-node reference imbalance | Date | Tue, 25 Jul 2017 12:18:40 -0700 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Johan Hovold <johan@kernel.org>
commit c592fafbdbb6b1279b76a54722d1465ca77e5bde upstream.
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: Laxman Dewangan <ldewangan@nvidia.com> Signed-off-by: Johan Hovold <johan@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/thermal/max77620_thermal.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
--- a/drivers/thermal/max77620_thermal.c +++ b/drivers/thermal/max77620_thermal.c @@ -104,8 +104,6 @@ static int max77620_thermal_probe(struct 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 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)) {
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