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, 45 insertions, 0 deletions

diff --git a/include/scsi/scsi_driver.h b/include/scsi/scsi_driver.h
new file mode 100644
index 000000000..249cea724
--- /dev/null
+++ b/include/scsi/scsi_driver.h
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCSI_SCSI_DRIVER_H
+#define _SCSI_SCSI_DRIVER_H
+
+#include <linux/blk_types.h>
+#include <linux/device.h>
+#include <scsi/scsi_cmnd.h>
+
+struct module;
+struct request;
+
+struct scsi_driver {
+	struct device_driver	gendrv;
+
+	int (*probe)(struct scsi_device *);
+	void (*remove)(struct scsi_device *);
+	void (*shutdown)(struct scsi_device *);
+	int (*resume)(struct device *);
+	void (*rescan)(struct device *);
+	blk_status_t (*init_command)(struct scsi_cmnd *);
+	void (*uninit_command)(struct scsi_cmnd *);
+	int (*done)(struct scsi_cmnd *);
+	int (*eh_action)(struct scsi_cmnd *, int);
+	void (*eh_reset)(struct scsi_cmnd *);
+};
+#define to_scsi_driver(drv) \
+	container_of((drv), struct scsi_driver, gendrv)
+
+#define scsi_register_driver(drv) \
+	__scsi_register_driver(drv, THIS_MODULE)
+int __scsi_register_driver(struct scsi_driver *, struct module *);
+#define scsi_unregister_driver(drv) \
+	driver_unregister(&(drv)->gendrv);
+
+extern int scsi_register_interface(struct class_interface *);
+#define scsi_unregister_interface(intf) \
+	class_interface_unregister(intf)
+
+/* make sure not to use it with passthrough commands */
+static inline struct scsi_driver *scsi_cmd_to_driver(struct scsi_cmnd *cmd)
+{
+	return to_scsi_driver(cmd->device->sdev_gendev.driver);
+}
+
+#endif /* _SCSI_SCSI_DRIVER_H */