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, 43 insertions, 0 deletions

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
new file mode 100644
index 000000000..f4583dcaf
--- /dev/null
+++ b/fs/sysfs/sysfs.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * fs/sysfs/sysfs.h - sysfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ */
+
+#ifndef __SYSFS_INTERNAL_H
+#define __SYSFS_INTERNAL_H
+
+#include <linux/sysfs.h>
+
+/*
+ * mount.c
+ */
+extern struct kernfs_node *sysfs_root_kn;
+
+/*
+ * dir.c
+ */
+extern spinlock_t sysfs_symlink_target_lock;
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name);
+
+/*
+ * file.c
+ */
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+		const struct attribute *attr, umode_t amode, kuid_t uid,
+		kgid_t gid, const struct ns_common *ns);
+int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
+		const struct bin_attribute *battr, umode_t mode, size_t size,
+		kuid_t uid, kgid_t gid, const struct ns_common *ns);
+
+/*
+ * symlink.c
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name);
+
+#endif	/* __SYSFS_INTERNAL_H */