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, 99 insertions, 0 deletions

diff --git a/lib/notifier-error-inject.c b/lib/notifier-error-inject.c
new file mode 100644
index 000000000..954c3412d
--- /dev/null
+++ b/lib/notifier-error-inject.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+
+#include "notifier-error-inject.h"
+
+static int debugfs_errno_set(void *data, u64 val)
+{
+	*(int *)data = clamp_t(int, val, -MAX_ERRNO, 0);
+	return 0;
+}
+
+static int debugfs_errno_get(void *data, u64 *val)
+{
+	*val = *(int *)data;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE_SIGNED(fops_errno, debugfs_errno_get, debugfs_errno_set,
+			"%lld\n");
+
+static struct dentry *debugfs_create_errno(const char *name, umode_t mode,
+				struct dentry *parent, int *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_errno);
+}
+
+static int notifier_err_inject_callback(struct notifier_block *nb,
+				unsigned long val, void *p)
+{
+	int err = 0;
+	struct notifier_err_inject *err_inject =
+		container_of(nb, struct notifier_err_inject, nb);
+	struct notifier_err_inject_action *action;
+
+	for (action = err_inject->actions; action->name; action++) {
+		if (action->val == val) {
+			err = action->error;
+			break;
+		}
+	}
+	if (err)
+		pr_info("Injecting error (%d) to %s\n", err, action->name);
+
+	return notifier_from_errno(err);
+}
+
+struct dentry *notifier_err_inject_dir;
+EXPORT_SYMBOL_GPL(notifier_err_inject_dir);
+
+struct dentry *notifier_err_inject_init(const char *name, struct dentry *parent,
+			struct notifier_err_inject *err_inject, int priority)
+{
+	struct notifier_err_inject_action *action;
+	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct dentry *dir;
+	struct dentry *actions_dir;
+
+	err_inject->nb.notifier_call = notifier_err_inject_callback;
+	err_inject->nb.priority = priority;
+
+	dir = debugfs_create_dir(name, parent);
+
+	actions_dir = debugfs_create_dir("actions", dir);
+
+	for (action = err_inject->actions; action->name; action++) {
+		struct dentry *action_dir;
+
+		action_dir = debugfs_create_dir(action->name, actions_dir);
+
+		/*
+		 * Create debugfs r/w file containing action->error. If
+		 * notifier call chain is called with action->val, it will
+		 * fail with the error code
+		 */
+		debugfs_create_errno("error", mode, action_dir, &action->error);
+	}
+	return dir;
+}
+EXPORT_SYMBOL_GPL(notifier_err_inject_init);
+
+static int __init err_inject_init(void)
+{
+	notifier_err_inject_dir =
+		debugfs_create_dir("notifier-error-inject", NULL);
+
+	return 0;
+}
+
+static void __exit err_inject_exit(void)
+{
+	debugfs_remove_recursive(notifier_err_inject_dir);
+}
+
+module_init(err_inject_init);
+module_exit(err_inject_exit);
+
+MODULE_DESCRIPTION("Notifier error injection module");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");