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, 140 insertions, 0 deletions

diff --git a/drivers/leds/trigger/ledtrig-backlight.c b/drivers/leds/trigger/ledtrig-backlight.c
new file mode 100644
index 000000000..e67bc7c2a
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-backlight.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight emulation LED trigger
+ *
+ * Copyright 2008 (C) Rodolfo Giometti <giometti@linux.it>
+ * Copyright 2008 (C) Eurotech S.p.A. <info@eurotech.it>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/leds.h>
+#include "../leds.h"
+
+#define BLANK		1
+#define UNBLANK		0
+
+struct bl_trig_notifier {
+	struct led_classdev *led;
+	int brightness;
+	int old_status;
+	unsigned invert;
+
+	struct list_head entry;
+};
+
+static DEFINE_MUTEX(ledtrig_backlight_list_mutex);
+static LIST_HEAD(ledtrig_backlight_list);
+
+static void ledtrig_backlight_notify_blank(struct bl_trig_notifier *n, int new_status)
+{
+	struct led_classdev *led = n->led;
+
+	if (new_status == n->old_status)
+		return;
+
+	if ((n->old_status == UNBLANK) ^ n->invert) {
+		n->brightness = led->brightness;
+		led_set_brightness_nosleep(led, LED_OFF);
+	} else {
+		led_set_brightness_nosleep(led, n->brightness);
+	}
+
+	n->old_status = new_status;
+}
+
+void ledtrig_backlight_blank(bool blank)
+{
+	struct bl_trig_notifier *n;
+	int new_status = blank ? BLANK : UNBLANK;
+
+	guard(mutex)(&ledtrig_backlight_list_mutex);
+
+	list_for_each_entry(n, &ledtrig_backlight_list, entry)
+		ledtrig_backlight_notify_blank(n, new_status);
+}
+EXPORT_SYMBOL(ledtrig_backlight_blank);
+
+static ssize_t bl_trig_invert_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
+
+	return sprintf(buf, "%u\n", n->invert);
+}
+
+static ssize_t bl_trig_invert_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t num)
+{
+	struct led_classdev *led = led_trigger_get_led(dev);
+	struct bl_trig_notifier *n = led_trigger_get_drvdata(dev);
+	unsigned long invert;
+	int ret;
+
+	ret = kstrtoul(buf, 10, &invert);
+	if (ret < 0)
+		return ret;
+
+	if (invert > 1)
+		return -EINVAL;
+
+	n->invert = invert;
+
+	/* After inverting, we need to update the LED. */
+	if ((n->old_status == BLANK) ^ n->invert)
+		led_set_brightness_nosleep(led, LED_OFF);
+	else
+		led_set_brightness_nosleep(led, n->brightness);
+
+	return num;
+}
+static DEVICE_ATTR(inverted, 0644, bl_trig_invert_show, bl_trig_invert_store);
+
+static struct attribute *bl_trig_attrs[] = {
+	&dev_attr_inverted.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(bl_trig);
+
+static int bl_trig_activate(struct led_classdev *led)
+{
+	struct bl_trig_notifier *n;
+
+	n = kzalloc_obj(struct bl_trig_notifier);
+	if (!n)
+		return -ENOMEM;
+	led_set_trigger_data(led, n);
+
+	n->led = led;
+	n->brightness = led->brightness;
+	n->old_status = UNBLANK;
+
+	guard(mutex)(&ledtrig_backlight_list_mutex);
+	list_add(&n->entry, &ledtrig_backlight_list);
+
+	return 0;
+}
+
+static void bl_trig_deactivate(struct led_classdev *led)
+{
+	struct bl_trig_notifier *n = led_get_trigger_data(led);
+
+	guard(mutex)(&ledtrig_backlight_list_mutex);
+	list_del(&n->entry);
+
+	kfree(n);
+}
+
+static struct led_trigger bl_led_trigger = {
+	.name		= "backlight",
+	.activate	= bl_trig_activate,
+	.deactivate	= bl_trig_deactivate,
+	.groups		= bl_trig_groups,
+};
+module_led_trigger(bl_led_trigger);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("Backlight emulation LED trigger");
+MODULE_LICENSE("GPL v2");