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, 100 insertions, 0 deletions

diff --git a/drivers/parisc/eisa_eeprom.c b/drivers/parisc/eisa_eeprom.c
new file mode 100644
index 000000000..2058b4c5b
--- /dev/null
+++ b/drivers/parisc/eisa_eeprom.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* 
+ *    EISA "eeprom" support routines
+ *
+ *    Copyright (C) 2001 Thomas Bogendoerfer <tsbogend at parisc-linux.org>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <asm/io.h>
+#include <linux/uaccess.h>
+#include <asm/eisa_eeprom.h>
+
+static loff_t eisa_eeprom_llseek(struct file *file, loff_t offset, int origin)
+{
+	return fixed_size_llseek(file, offset, origin, HPEE_MAX_LENGTH);
+}
+
+static ssize_t eisa_eeprom_read(struct file * file,
+			      char __user *buf, size_t count, loff_t *ppos )
+{
+	unsigned char *tmp;
+	ssize_t ret;
+	int i;
+	
+	if (*ppos < 0 || *ppos >= HPEE_MAX_LENGTH)
+		return 0;
+	
+	count = *ppos + count < HPEE_MAX_LENGTH ? count : HPEE_MAX_LENGTH - *ppos;
+	tmp = kmalloc(count, GFP_KERNEL);
+	if (tmp) {
+		for (i = 0; i < count; i++)
+			tmp[i] = readb(eisa_eeprom_addr+(*ppos)++);
+
+		if (copy_to_user (buf, tmp, count))
+			ret = -EFAULT;
+		else
+			ret = count;
+		kfree (tmp);
+	} else
+		ret = -ENOMEM;
+	
+	return ret;
+}
+
+static int eisa_eeprom_open(struct inode *inode, struct file *file)
+{
+	if (file->f_mode & FMODE_WRITE)
+		return -EINVAL;
+   
+	return 0;
+}
+
+static int eisa_eeprom_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+/*
+ *	The various file operations we support.
+ */
+static const struct file_operations eisa_eeprom_fops = {
+	.owner =	THIS_MODULE,
+	.llseek =	eisa_eeprom_llseek,
+	.read =		eisa_eeprom_read,
+	.open =		eisa_eeprom_open,
+	.release =	eisa_eeprom_release,
+};
+
+static struct miscdevice eisa_eeprom_dev = {
+	EISA_EEPROM_MINOR,
+	"eisa_eeprom",
+	&eisa_eeprom_fops
+};
+
+static int __init eisa_eeprom_init(void)
+{
+	int retval;
+
+	if (!eisa_eeprom_addr)
+		return -ENODEV;
+
+	retval = misc_register(&eisa_eeprom_dev);
+	if (retval < 0) {
+		printk(KERN_ERR "EISA EEPROM: cannot register misc device.\n");
+		return retval;
+	}
+
+	printk(KERN_INFO "EISA EEPROM at 0x%px\n", eisa_eeprom_addr);
+	return 0;
+}
+
+MODULE_DESCRIPTION("EISA eeprom driver");
+MODULE_LICENSE("GPL");
+
+module_init(eisa_eeprom_init);