[PATCH v5.10] drivers: base: Free devm resources when unregistering a device

[PATCH v5.10] drivers: base: Free devm resources when unregistering a device

[Brennan Lamoreaux]

From: David Gow <davidgow@google.com>

[ Upstream commit 699fb50d99039a50e7494de644f96c889279aca3 ]

In the current code, devres_release_all() only gets called if the device
has a bus and has been probed.

This leads to issues when using bus-less or driver-less devices where
the device might never get freed if a managed resource holds a reference
to the device. This is happening in the DRM framework for example.

We should thus call devres_release_all() in the device_del() function to
make sure that the device-managed actions are properly executed when the
device is unregistered, even if it has neither a bus nor a driver.

This is effectively the same change than commit 2f8d16a996da ("devres:
release resources on device_del()") that got reverted by commit
a525a3ddeaca ("driver core: free devres in device_release") over
memory leaks concerns.

This patch effectively combines the two commits mentioned above to
release the resources both on device_del() and device_release() and get
the best of both worlds.

Fixes: a525a3ddeaca ("driver core: free devres in device_release")
Signed-off-by: David Gow <davidgow@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20230720-kunit-devm-inconsistencies-test-v3-3-6aa7e074f373@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Brennan Lamoreaux <brennan.lamoreaux@broadcom.com>
---
 drivers/base/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 82eb25ad1..3f38e4aa6 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3194,6 +3194,17 @@ void device_del(struct device *dev)
 	device_remove_properties(dev);
 	device_links_purge(dev);

+	/*
+	 * If a device does not have a driver attached, we need to clean
+	 * up any managed resources. We do this in device_release(), but
+	 * it's never called (and we leak the device) if a managed
+	 * resource holds a reference to the device. So release all
+	 * managed resources here, like we do in driver_detach(). We
+	 * still need to do so again in device_release() in case someone
+	 * adds a new resource after this point, though.
+	 */
+	devres_release_all(dev);
+
 	if (dev->bus)
 		blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
 					     BUS_NOTIFY_REMOVED_DEVICE, dev);
--
2.43.7