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, 355 insertions, 0 deletions

diff --git a/drivers/usb/misc/cytherm.c b/drivers/usb/misc/cytherm.c
new file mode 100644
index 000000000..b183df982
--- /dev/null
+++ b/drivers/usb/misc/cytherm.c
@@ -0,0 +1,355 @@
+// SPDX-License-Identifier: GPL-2.0
+/* -*- linux-c -*-
+ * Cypress USB Thermometer driver 
+ * 
+ * Copyright (c) 2004 Erik Rigtorp <erkki@linux.nu> <erik@rigtorp.com>
+ * 
+ * This driver works with Elektor magazine USB Interface as published in 
+ * issue #291. It should also work with the original starter kit/demo board
+ * from Cypress.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+
+#define DRIVER_AUTHOR "Erik Rigtorp"
+#define DRIVER_DESC "Cypress USB Thermometer driver"
+
+#define USB_SKEL_VENDOR_ID	0x04b4
+#define USB_SKEL_PRODUCT_ID	0x0002
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
+	{ }
+};
+MODULE_DEVICE_TABLE (usb, id_table);
+
+/* Structure to hold all of our device specific stuff */
+struct usb_cytherm {
+	struct usb_device    *udev;	 /* save off the usb device pointer */
+	struct usb_interface *interface; /* the interface for this device */
+	int brightness;
+};
+
+
+/* Vendor requests */
+/* They all operate on one byte at a time */
+#define PING       0x00
+#define READ_ROM   0x01 /* Reads form ROM, value = address */
+#define READ_RAM   0x02 /* Reads form RAM, value = address */
+#define WRITE_RAM  0x03 /* Write to RAM, value = address, index = data */
+#define READ_PORT  0x04 /* Reads from port, value = address */
+#define WRITE_PORT 0x05 /* Write to port, value = address, index = data */ 
+
+
+/* Send a vendor command to device */
+static int vendor_command(struct usb_device *dev, unsigned char request, 
+			  unsigned char value, unsigned char index,
+			  void *buf, int size)
+{
+	return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+			       request, 
+			       USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
+			       value, 
+			       index, buf, size,
+			       USB_CTRL_GET_TIMEOUT);
+}
+
+
+
+#define BRIGHTNESS 0x2c     /* RAM location for brightness value */
+#define BRIGHTNESS_SEM 0x2b /* RAM location for brightness semaphore */
+
+static ssize_t brightness_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);    
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);     
+
+	return sprintf(buf, "%i", cytherm->brightness);
+}
+
+static ssize_t brightness_store(struct device *dev, struct device_attribute *attr, const char *buf,
+			      size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	cytherm->brightness = simple_strtoul(buf, NULL, 10);
+   
+	if (cytherm->brightness > 0xFF)
+		cytherm->brightness = 0xFF;
+	else if (cytherm->brightness < 0)
+		cytherm->brightness = 0;
+   
+	/* Set brightness */
+	retval = vendor_command(cytherm->udev, WRITE_RAM, BRIGHTNESS, 
+				cytherm->brightness, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	/* Inform µC that we have changed the brightness setting */
+	retval = vendor_command(cytherm->udev, WRITE_RAM, BRIGHTNESS_SEM,
+				0x01, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	kfree(buffer);
+   
+	return count;
+}
+static DEVICE_ATTR_RW(brightness);
+
+
+#define TEMP 0x33 /* RAM location for temperature */
+#define SIGN 0x34 /* RAM location for temperature sign */
+
+static ssize_t temp_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	int temp, sign;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	/* read temperature */
+	retval = vendor_command(cytherm->udev, READ_RAM, TEMP, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	temp = buffer[1];
+   
+	/* read sign */
+	retval = vendor_command(cytherm->udev, READ_RAM, SIGN, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	sign = buffer[1];
+
+	kfree(buffer);
+   
+	return sprintf(buf, "%c%i.%i", sign ? '-' : '+', temp >> 1,
+		       5*(temp - ((temp >> 1) << 1)));
+}
+static DEVICE_ATTR_RO(temp);
+
+
+#define BUTTON 0x7a
+
+static ssize_t button_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	/* check button */
+	retval = vendor_command(cytherm->udev, READ_RAM, BUTTON, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	if (retval)
+		return sprintf(buf, "1");
+	else
+		return sprintf(buf, "0");
+}
+static DEVICE_ATTR_RO(button);
+
+
+static ssize_t port0_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	retval = vendor_command(cytherm->udev, READ_PORT, 0, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	return sprintf(buf, "%d", retval);
+}
+
+
+static ssize_t port0_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+	int tmp;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	tmp = simple_strtoul(buf, NULL, 10);
+   
+	if (tmp > 0xFF)
+		tmp = 0xFF;
+	else if (tmp < 0)
+		tmp = 0;
+   
+	retval = vendor_command(cytherm->udev, WRITE_PORT, 0,
+				tmp, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	kfree(buffer);
+
+	return count;
+}
+static DEVICE_ATTR_RW(port0);
+
+static ssize_t port1_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	retval = vendor_command(cytherm->udev, READ_PORT, 1, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	return sprintf(buf, "%d", retval);
+}
+
+
+static ssize_t port1_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+	int tmp;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	tmp = simple_strtoul(buf, NULL, 10);
+   
+	if (tmp > 0xFF)
+		tmp = 0xFF;
+	else if (tmp < 0)
+		tmp = 0;
+   
+	retval = vendor_command(cytherm->udev, WRITE_PORT, 1,
+				tmp, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	kfree(buffer);
+
+	return count;
+}
+static DEVICE_ATTR_RW(port1);
+
+static struct attribute *cytherm_attrs[] = {
+	&dev_attr_brightness.attr,
+	&dev_attr_temp.attr,
+	&dev_attr_button.attr,
+	&dev_attr_port0.attr,
+	&dev_attr_port1.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cytherm);
+
+static int cytherm_probe(struct usb_interface *interface, 
+			 const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct usb_cytherm *dev;
+	int retval = -ENOMEM;
+
+	dev = kzalloc_obj(struct usb_cytherm);
+	if (!dev)
+		goto error_mem;
+
+	dev->udev = udev;
+
+	usb_set_intfdata(interface, dev);
+
+	dev->brightness = 0xFF;
+
+	dev_info(&interface->dev,
+		  "Cypress thermometer device now attached\n");
+	return 0;
+
+error_mem:
+	return retval;
+}
+
+static void cytherm_disconnect(struct usb_interface *interface)
+{
+	struct usb_cytherm *dev;
+
+	dev = usb_get_intfdata(interface);
+
+	/* first remove the files, then NULL the pointer */
+	usb_set_intfdata(interface, NULL);
+
+	kfree(dev);
+
+	dev_info(&interface->dev, "Cypress thermometer now disconnected\n");
+}
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver cytherm_driver = {
+	.name =		"cytherm",
+	.probe =	cytherm_probe,
+	.disconnect =	cytherm_disconnect,
+	.id_table =	id_table,
+	.dev_groups =	cytherm_groups,
+};
+
+module_usb_driver(cytherm_driver);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");