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, 94 insertions, 0 deletions

diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c
new file mode 100644
index 000000000..0fdd581ef
--- /dev/null
+++ b/drivers/acpi/bgrt.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * BGRT boot graphic support
+ * Authors: Matthew Garrett, Josh Triplett <josh@joshtriplett.org>
+ * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
+ * Copyright 2012 Intel Corporation
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/sysfs.h>
+#include <linux/efi-bgrt.h>
+
+static void *bgrt_image;
+static struct kobject *bgrt_kobj;
+
+#define BGRT_SHOW(_name, _member) \
+	static ssize_t _name##_show(struct kobject *kobj,			\
+				    struct kobj_attribute *attr, char *buf)	\
+	{									\
+		return sysfs_emit(buf, "%d\n", bgrt_tab._member);		\
+	}									\
+	static struct kobj_attribute bgrt_attr_##_name = __ATTR_RO(_name)
+
+BGRT_SHOW(version, version);
+BGRT_SHOW(status, status);
+BGRT_SHOW(type, image_type);
+BGRT_SHOW(xoffset, image_offset_x);
+BGRT_SHOW(yoffset, image_offset_y);
+
+static __ro_after_init BIN_ATTR_SIMPLE_RO(image);
+
+static struct attribute *bgrt_attributes[] = {
+	&bgrt_attr_version.attr,
+	&bgrt_attr_status.attr,
+	&bgrt_attr_type.attr,
+	&bgrt_attr_xoffset.attr,
+	&bgrt_attr_yoffset.attr,
+	NULL,
+};
+
+static const struct bin_attribute *const bgrt_bin_attributes[] = {
+	&bin_attr_image,
+	NULL,
+};
+
+static const struct attribute_group bgrt_attribute_group = {
+	.attrs = bgrt_attributes,
+	.bin_attrs = bgrt_bin_attributes,
+};
+
+int __init acpi_parse_bgrt(struct acpi_table_header *table)
+{
+	efi_bgrt_init(table);
+	return 0;
+}
+
+static int __init bgrt_init(void)
+{
+	int ret;
+
+	if (!bgrt_tab.image_address)
+		return -ENODEV;
+
+	bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size,
+			      MEMREMAP_WB);
+	if (!bgrt_image) {
+		pr_notice("Ignoring BGRT: failed to map image memory\n");
+		return -ENOMEM;
+	}
+
+	bin_attr_image.private = bgrt_image;
+	bin_attr_image.size = bgrt_image_size;
+
+	bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj);
+	if (!bgrt_kobj) {
+		ret = -EINVAL;
+		goto out_memmap;
+	}
+
+	ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group);
+	if (ret)
+		goto out_kobject;
+
+	return 0;
+
+out_kobject:
+	kobject_put(bgrt_kobj);
+out_memmap:
+	memunmap(bgrt_image);
+	return ret;
+}
+device_initcall(bgrt_init);