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, 214 insertions, 0 deletions

diff --git a/drivers/gnss/usb.c b/drivers/gnss/usb.c
new file mode 100644
index 000000000..0d9dde023
--- /dev/null
+++ b/drivers/gnss/usb.c
@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic USB GNSS receiver driver
+ *
+ * Copyright (C) 2021 Johan Hovold <johan@kernel.org>
+ */
+
+#include <linux/errno.h>
+#include <linux/gnss.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/usb.h>
+
+#define GNSS_USB_READ_BUF_LEN	512
+#define GNSS_USB_WRITE_TIMEOUT	1000
+
+static const struct usb_device_id gnss_usb_id_table[] = {
+	{ USB_DEVICE(0x1199, 0xb000) },		/* Sierra Wireless XM1210 */
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, gnss_usb_id_table);
+
+struct gnss_usb {
+	struct usb_device *udev;
+	struct usb_interface *intf;
+	struct gnss_device *gdev;
+	struct urb *read_urb;
+	unsigned int write_pipe;
+};
+
+static void gnss_usb_rx_complete(struct urb *urb)
+{
+	struct gnss_usb *gusb = urb->context;
+	struct gnss_device *gdev = gusb->gdev;
+	int status = urb->status;
+	int len;
+	int ret;
+
+	switch (status) {
+	case 0:
+		break;
+	case -ENOENT:
+	case -ECONNRESET:
+	case -ESHUTDOWN:
+		dev_dbg(&gdev->dev, "urb stopped: %d\n", status);
+		return;
+	case -EPIPE:
+		dev_err(&gdev->dev, "urb stopped: %d\n", status);
+		return;
+	default:
+		dev_dbg(&gdev->dev, "nonzero urb status: %d\n", status);
+		goto resubmit;
+	}
+
+	len = urb->actual_length;
+	if (len == 0)
+		goto resubmit;
+
+	ret = gnss_insert_raw(gdev, urb->transfer_buffer, len);
+	if (ret < len)
+		dev_dbg(&gdev->dev, "dropped %d bytes\n", len - ret);
+resubmit:
+	ret = usb_submit_urb(urb, GFP_ATOMIC);
+	if (ret && ret != -EPERM && ret != -ENODEV)
+		dev_err(&gdev->dev, "failed to resubmit urb: %d\n", ret);
+}
+
+static int gnss_usb_open(struct gnss_device *gdev)
+{
+	struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+	int ret;
+
+	ret = usb_submit_urb(gusb->read_urb, GFP_KERNEL);
+	if (ret) {
+		if (ret != -EPERM && ret != -ENODEV)
+			dev_err(&gdev->dev, "failed to submit urb: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void gnss_usb_close(struct gnss_device *gdev)
+{
+	struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+
+	usb_kill_urb(gusb->read_urb);
+}
+
+static int gnss_usb_write_raw(struct gnss_device *gdev,
+		const unsigned char *buf, size_t count)
+{
+	struct gnss_usb *gusb = gnss_get_drvdata(gdev);
+	void *tbuf;
+	int ret;
+
+	tbuf = kmemdup(buf, count, GFP_KERNEL);
+	if (!tbuf)
+		return -ENOMEM;
+
+	ret = usb_bulk_msg(gusb->udev, gusb->write_pipe, tbuf, count, NULL,
+			GNSS_USB_WRITE_TIMEOUT);
+	kfree(tbuf);
+	if (ret)
+		return ret;
+
+	return count;
+}
+
+static const struct gnss_operations gnss_usb_gnss_ops = {
+	.open		= gnss_usb_open,
+	.close		= gnss_usb_close,
+	.write_raw	= gnss_usb_write_raw,
+};
+
+static int gnss_usb_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct usb_endpoint_descriptor *in, *out;
+	struct gnss_device *gdev;
+	struct gnss_usb *gusb;
+	struct urb *urb;
+	size_t buf_len;
+	void *buf;
+	int ret;
+
+	ret = usb_find_common_endpoints(intf->cur_altsetting, &in, &out, NULL,
+			NULL);
+	if (ret)
+		return ret;
+
+	gusb = kzalloc_obj(*gusb);
+	if (!gusb)
+		return -ENOMEM;
+
+	gdev = gnss_allocate_device(&intf->dev);
+	if (!gdev) {
+		ret = -ENOMEM;
+		goto err_free_gusb;
+	}
+
+	gdev->ops = &gnss_usb_gnss_ops;
+	gdev->type = GNSS_TYPE_NMEA;
+	gnss_set_drvdata(gdev, gusb);
+
+	urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!urb) {
+		ret = -ENOMEM;
+		goto err_put_gdev;
+	}
+
+	buf_len = max(usb_endpoint_maxp(in), GNSS_USB_READ_BUF_LEN);
+
+	buf = kzalloc(buf_len, GFP_KERNEL);
+	if (!buf) {
+		ret = -ENOMEM;
+		goto err_free_urb;
+	}
+
+	usb_fill_bulk_urb(urb, udev,
+			usb_rcvbulkpipe(udev, usb_endpoint_num(in)),
+			buf, buf_len, gnss_usb_rx_complete, gusb);
+
+	gusb->intf = intf;
+	gusb->udev = udev;
+	gusb->gdev = gdev;
+	gusb->read_urb = urb;
+	gusb->write_pipe = usb_sndbulkpipe(udev, usb_endpoint_num(out));
+
+	ret = gnss_register_device(gdev);
+	if (ret)
+		goto err_free_buf;
+
+	usb_set_intfdata(intf, gusb);
+
+	return 0;
+
+err_free_buf:
+	kfree(buf);
+err_free_urb:
+	usb_free_urb(urb);
+err_put_gdev:
+	gnss_put_device(gdev);
+err_free_gusb:
+	kfree(gusb);
+
+	return ret;
+}
+
+static void gnss_usb_disconnect(struct usb_interface *intf)
+{
+	struct gnss_usb *gusb = usb_get_intfdata(intf);
+
+	gnss_deregister_device(gusb->gdev);
+
+	kfree(gusb->read_urb->transfer_buffer);
+	usb_free_urb(gusb->read_urb);
+	gnss_put_device(gusb->gdev);
+	kfree(gusb);
+}
+
+static struct usb_driver gnss_usb_driver = {
+	.name		= "gnss-usb",
+	.probe		= gnss_usb_probe,
+	.disconnect	= gnss_usb_disconnect,
+	.id_table	= gnss_usb_id_table,
+};
+module_usb_driver(gnss_usb_driver);
+
+MODULE_AUTHOR("Johan Hovold <johan@kernel.org>");
+MODULE_DESCRIPTION("Generic USB GNSS receiver driver");
+MODULE_LICENSE("GPL v2");