x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 146 insertions, 0 deletions

diff --git a/lib/kunit/fwnode.c b/lib/kunit/fwnode.c
new file mode 100644
index 000000000..a58ce0984
--- /dev/null
+++ b/lib/kunit/fwnode.c
@@ -0,0 +1,146 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Qualcomm Technologies, Inc. and/or its subsidiaries
+ */
+
+#include <kunit/fwnode.h>
+#include <kunit/test.h>
+
+#include <linux/fwnode.h>
+#include <linux/property.h>
+
+KUNIT_DEFINE_ACTION_WRAPPER(fwnode_remove_software_node_wrapper,
+			    fwnode_remove_software_node,
+			    struct fwnode_handle *);
+
+/**
+ * kunit_fwnode_create_software_node() - Create a kunit-managed software node
+ * @test: Test context
+ * @properties: Properties to use to create the new software node
+ * @parent: Parent of this software node
+ *
+ * Create a test-managed software node and return its firmware node handle.
+ * The software node is removed after the test case completes.
+ *
+ * Returns:
+ * Firmware node handle of the newly created software node or IS_ERR() on
+ * failure.
+ */
+struct fwnode_handle *
+kunit_fwnode_create_software_node(struct kunit *test,
+				  const struct property_entry *properties,
+				  const struct fwnode_handle *parent)
+{
+	struct fwnode_handle *fwnode;
+	int ret;
+
+	fwnode = fwnode_create_software_node(properties, parent);
+	if (IS_ERR(fwnode))
+		return fwnode;
+
+	ret = kunit_add_action_or_reset(test, fwnode_remove_software_node_wrapper,
+					fwnode);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return fwnode;
+}
+EXPORT_SYMBOL_GPL(kunit_fwnode_create_software_node);
+
+KUNIT_DEFINE_ACTION_WRAPPER(software_node_unregister_wrapper,
+			    software_node_unregister,
+			    const struct software_node *);
+
+/**
+ * kunit_software_node_register() - Register a kunit-managed software node
+ * @test: Test context
+ * @swnode: Software node to register
+ *
+ * Register a test-managed software node and return its firmware node handle.
+ * The software node is unregistered after the test case completes.
+ *
+ * Returns:
+ * Firmware node handle of the registered software node or IS_ERR() on failure.
+ */
+struct fwnode_handle *
+kunit_software_node_register(struct kunit *test,
+			     const struct software_node *swnode)
+{
+	struct fwnode_handle *fwnode;
+	int ret;
+
+	ret = software_node_register(swnode);
+	if (ret)
+		return ERR_PTR(ret);
+
+	fwnode = software_node_fwnode(swnode);
+	if (WARN_ON(!fwnode))
+		return ERR_PTR(-ENOENT);
+
+	ret = kunit_add_action_or_reset(test, software_node_unregister_wrapper,
+					(void *)swnode);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return fwnode;
+}
+EXPORT_SYMBOL_GPL(kunit_software_node_register);
+
+KUNIT_DEFINE_ACTION_WRAPPER(software_node_unregister_node_group_wrapper,
+			    software_node_unregister_node_group,
+			    const struct software_node *const *);
+
+/**
+ * kunit_software_node_register_node_group() - Register a kunit-managed software node group
+ * @test: Test context
+ * @nodes: Software node group to register
+ *
+ * Register a test-managed software node group. The nodes are unregistered
+ * after the test case completes.
+ *
+ * Returns:
+ * 0 on success, negative error number on failure.
+ */
+int kunit_software_node_register_node_group(struct kunit *test,
+					    const struct software_node *const *nodes)
+{
+	int ret;
+
+	ret = software_node_register_node_group(nodes);
+	if (ret)
+		return ret;
+
+	return kunit_add_action_or_reset(test, software_node_unregister_node_group_wrapper,
+					 (void *)nodes);
+}
+EXPORT_SYMBOL_GPL(kunit_software_node_register_node_group);
+
+KUNIT_DEFINE_ACTION_WRAPPER(device_remove_software_node_wrapper,
+			    device_remove_software_node,
+			    struct device *);
+
+/**
+ * kunit_device_add_software_node() - Assign a kunit-managed software node to a device
+ * @test: Test context
+ * @dev: Device to assign the software node for
+ * @node: The software node to assign
+ *
+ * Make @node the secondary firmware node of @dev. If @dev has no primary
+ * firmware node, @node will become the primary node. The software node will
+ * be automatically removed from @dev when the test case completes.
+ *
+ * Returns:
+ * 0 on success, negative error number on failure.
+ */
+int kunit_device_add_software_node(struct kunit *test, struct device *dev,
+				   const struct software_node *node)
+{
+	int ret;
+
+	ret = device_add_software_node(dev, node);
+	if (ret)
+		return ret;
+
+	return kunit_add_action_or_reset(test, device_remove_software_node_wrapper, dev);
+}
+EXPORT_SYMBOL_GPL(kunit_device_add_software_node);