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, 212 insertions, 0 deletions

diff --git a/drivers/nfc/virtual_ncidev.c b/drivers/nfc/virtual_ncidev.c
new file mode 100644
index 000000000..8eeb447ac
--- /dev/null
+++ b/drivers/nfc/virtual_ncidev.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Virtual NCI device simulation driver
+ *
+ * Copyright (C) 2020 Samsung Electronics
+ * Bongsu Jeon <bongsu.jeon@samsung.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/wait.h>
+#include <net/nfc/nci_core.h>
+
+#define IOCTL_GET_NCIDEV_IDX    0
+#define VIRTUAL_NFC_PROTOCOLS	(NFC_PROTO_JEWEL_MASK | \
+				 NFC_PROTO_MIFARE_MASK | \
+				 NFC_PROTO_FELICA_MASK | \
+				 NFC_PROTO_ISO14443_MASK | \
+				 NFC_PROTO_ISO14443_B_MASK | \
+				 NFC_PROTO_ISO15693_MASK)
+
+struct virtual_nci_dev {
+	struct nci_dev *ndev;
+	struct mutex mtx;
+	struct sk_buff *send_buff;
+	struct wait_queue_head wq;
+	bool running;
+};
+
+static int virtual_nci_open(struct nci_dev *ndev)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	vdev->running = true;
+	return 0;
+}
+
+static int virtual_nci_close(struct nci_dev *ndev)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	mutex_lock(&vdev->mtx);
+	kfree_skb(vdev->send_buff);
+	vdev->send_buff = NULL;
+	vdev->running = false;
+	mutex_unlock(&vdev->mtx);
+
+	return 0;
+}
+
+static int virtual_nci_send(struct nci_dev *ndev, struct sk_buff *skb)
+{
+	struct virtual_nci_dev *vdev = nci_get_drvdata(ndev);
+
+	mutex_lock(&vdev->mtx);
+	if (vdev->send_buff || !vdev->running) {
+		mutex_unlock(&vdev->mtx);
+		kfree_skb(skb);
+		return -1;
+	}
+	vdev->send_buff = skb_copy(skb, GFP_KERNEL);
+	if (!vdev->send_buff) {
+		mutex_unlock(&vdev->mtx);
+		kfree_skb(skb);
+		return -1;
+	}
+	mutex_unlock(&vdev->mtx);
+	wake_up_interruptible(&vdev->wq);
+	consume_skb(skb);
+
+	return 0;
+}
+
+static const struct nci_ops virtual_nci_ops = {
+	.open = virtual_nci_open,
+	.close = virtual_nci_close,
+	.send = virtual_nci_send
+};
+
+static ssize_t virtual_ncidev_read(struct file *file, char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	size_t actual_len;
+
+	mutex_lock(&vdev->mtx);
+	while (!vdev->send_buff) {
+		mutex_unlock(&vdev->mtx);
+		if (wait_event_interruptible(vdev->wq, vdev->send_buff))
+			return -EFAULT;
+		mutex_lock(&vdev->mtx);
+	}
+
+	actual_len = min_t(size_t, count, vdev->send_buff->len);
+
+	if (copy_to_user(buf, vdev->send_buff->data, actual_len)) {
+		mutex_unlock(&vdev->mtx);
+		return -EFAULT;
+	}
+
+	skb_pull(vdev->send_buff, actual_len);
+	if (vdev->send_buff->len == 0) {
+		consume_skb(vdev->send_buff);
+		vdev->send_buff = NULL;
+	}
+	mutex_unlock(&vdev->mtx);
+
+	return actual_len;
+}
+
+static ssize_t virtual_ncidev_write(struct file *file,
+				    const char __user *buf,
+				    size_t count, loff_t *ppos)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	struct sk_buff *skb;
+
+	skb = alloc_skb(count, GFP_KERNEL);
+	if (!skb)
+		return -ENOMEM;
+
+	if (copy_from_user(skb_put(skb, count), buf, count)) {
+		kfree_skb(skb);
+		return -EFAULT;
+	}
+
+	nci_recv_frame(vdev->ndev, skb);
+	return count;
+}
+
+static int virtual_ncidev_open(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+	struct virtual_nci_dev *vdev;
+
+	vdev = kzalloc_obj(*vdev);
+	if (!vdev)
+		return -ENOMEM;
+	vdev->ndev = nci_allocate_device(&virtual_nci_ops,
+		VIRTUAL_NFC_PROTOCOLS, 0, 0);
+	if (!vdev->ndev) {
+		kfree(vdev);
+		return -ENOMEM;
+	}
+
+	mutex_init(&vdev->mtx);
+	init_waitqueue_head(&vdev->wq);
+	file->private_data = vdev;
+	nci_set_drvdata(vdev->ndev, vdev);
+
+	ret = nci_register_device(vdev->ndev);
+	if (ret < 0) {
+		nci_free_device(vdev->ndev);
+		mutex_destroy(&vdev->mtx);
+		kfree(vdev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int virtual_ncidev_close(struct inode *inode, struct file *file)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+
+	nci_unregister_device(vdev->ndev);
+	nci_free_device(vdev->ndev);
+	mutex_destroy(&vdev->mtx);
+	kfree(vdev);
+
+	return 0;
+}
+
+static long virtual_ncidev_ioctl(struct file *file, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct virtual_nci_dev *vdev = file->private_data;
+	const struct nfc_dev *nfc_dev = vdev->ndev->nfc_dev;
+	void __user *p = (void __user *)arg;
+
+	if (cmd != IOCTL_GET_NCIDEV_IDX)
+		return -ENOTTY;
+
+	if (copy_to_user(p, &nfc_dev->idx, sizeof(nfc_dev->idx)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static const struct file_operations virtual_ncidev_fops = {
+	.owner = THIS_MODULE,
+	.read = virtual_ncidev_read,
+	.write = virtual_ncidev_write,
+	.open = virtual_ncidev_open,
+	.release = virtual_ncidev_close,
+	.unlocked_ioctl = virtual_ncidev_ioctl
+};
+
+static struct miscdevice miscdev = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "virtual_nci",
+	.fops = &virtual_ncidev_fops,
+	.mode = 0600,
+};
+
+module_misc_device(miscdev);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Virtual NCI device simulation driver");
+MODULE_AUTHOR("Bongsu Jeon <bongsu.jeon@samsung.com>");