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, 61 insertions, 0 deletions

diff --git a/drivers/thunderbolt/configfs.c b/drivers/thunderbolt/configfs.c
new file mode 100644
index 000000000..dc6bc363d
--- /dev/null
+++ b/drivers/thunderbolt/configfs.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ConfigFS support
+ *
+ * Copyright (C) 2026, Intel Corporation
+ * Author: Mika Westerberg <mika.westerberg@linux.intel.com>
+ */
+
+#include <linux/configfs.h>
+#include <linux/export.h>
+
+#include "tb.h"
+
+static const struct config_item_type tb_root_group_type = {
+	.ct_owner = THIS_MODULE,
+};
+
+static struct configfs_subsystem tb_configfs = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "thunderbolt",
+			.ci_type = &tb_root_group_type,
+		},
+	},
+};
+
+/**
+ * tb_configfs_register_group() - Register Thunderbolt ConfigFS group
+ * @group: Group to register.
+ *
+ * Registers the new @group under Thunderbolt subsystem ConfigFS.
+ *
+ * Return: 0% in case of success, negative errno otherwise.
+ */
+int tb_configfs_register_group(struct config_group *group)
+{
+	return configfs_register_group(&tb_configfs.su_group, group);
+}
+EXPORT_SYMBOL_GPL(tb_configfs_register_group);
+
+/**
+ * tb_configfs_unregister_group() - Unregister previously registered group
+ * @group: Group to unregister.
+ */
+void tb_configfs_unregister_group(struct config_group *group)
+{
+	configfs_unregister_group(group);
+}
+EXPORT_SYMBOL_GPL(tb_configfs_unregister_group);
+
+int tb_configfs_init(void)
+{
+	config_group_init(&tb_configfs.su_group);
+	mutex_init(&tb_configfs.su_mutex);
+	return configfs_register_subsystem(&tb_configfs);
+}
+
+void tb_configfs_exit(void)
+{
+	configfs_unregister_subsystem(&tb_configfs);
+}