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, 191 insertions, 0 deletions

diff --git a/drivers/usb/serial/symbolserial.c b/drivers/usb/serial/symbolserial.c
new file mode 100644
index 000000000..8823671a9
--- /dev/null
+++ b/drivers/usb/serial/symbolserial.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Symbol USB barcode to serial driver
+ *
+ * Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
+ * Copyright (C) 2009 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (C) 2009 Novell Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/slab.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(0x05e0, 0x0600) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+struct symbol_private {
+	spinlock_t lock;	/* protects the following flags */
+	bool throttled;
+	bool actually_throttled;
+};
+
+static void symbol_int_callback(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned char *data = urb->transfer_buffer;
+	int status = urb->status;
+	unsigned long flags;
+	int result;
+	int data_length;
+
+	switch (status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
+			__func__, status);
+		goto exit;
+	}
+
+	usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
+
+	/*
+	 * Data from the device comes with a 1 byte header:
+	 *
+	 * <size of data> <data>...
+	 */
+	if (urb->actual_length > 1) {
+		data_length = data[0];
+		if (data_length > (urb->actual_length - 1))
+			data_length = urb->actual_length - 1;
+		tty_insert_flip_string(&port->port, &data[1], data_length);
+		tty_flip_buffer_push(&port->port);
+	} else {
+		dev_dbg(&port->dev, "%s - short packet\n", __func__);
+	}
+
+exit:
+	spin_lock_irqsave(&priv->lock, flags);
+
+	/* Continue trying to always read if we should */
+	if (!priv->throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
+		if (result)
+			dev_err(&port->dev,
+			    "%s - failed resubmitting read urb, error %d\n",
+							__func__, result);
+	} else
+		priv->actually_throttled = true;
+	spin_unlock_irqrestore(&priv->lock, flags);
+}
+
+static int symbol_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	int result = 0;
+
+	spin_lock_irqsave(&priv->lock, flags);
+	priv->throttled = false;
+	priv->actually_throttled = false;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	/* Start reading from the device */
+	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+	if (result)
+		dev_err(&port->dev,
+			"%s - failed resubmitting read urb, error %d\n",
+			__func__, result);
+	return result;
+}
+
+static void symbol_close(struct usb_serial_port *port)
+{
+	usb_kill_urb(port->interrupt_in_urb);
+}
+
+static void symbol_throttle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = true;
+	spin_unlock_irq(&priv->lock);
+}
+
+static void symbol_unthrottle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	int result;
+	bool was_throttled;
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = false;
+	was_throttled = priv->actually_throttled;
+	priv->actually_throttled = false;
+	spin_unlock_irq(&priv->lock);
+
+	if (was_throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+		if (result)
+			dev_err(&port->dev,
+				"%s - failed submitting read urb, error %d\n",
+							__func__, result);
+	}
+}
+
+static int symbol_port_probe(struct usb_serial_port *port)
+{
+	struct symbol_private *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+
+	usb_set_serial_port_data(port, priv);
+
+	return 0;
+}
+
+static void symbol_port_remove(struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	kfree(priv);
+}
+
+static struct usb_serial_driver symbol_device = {
+	.driver = {
+		.name =		"symbol",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.num_interrupt_in =	1,
+	.port_probe =		symbol_port_probe,
+	.port_remove =		symbol_port_remove,
+	.open =			symbol_open,
+	.close =		symbol_close,
+	.throttle = 		symbol_throttle,
+	.unthrottle =		symbol_unthrottle,
+	.read_int_callback =	symbol_int_callback,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&symbol_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_DESCRIPTION("Symbol USB barcode to serial driver");
+MODULE_LICENSE("GPL v2");