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, 139 insertions, 0 deletions

diff --git a/include/drm/drm_auth.h b/include/drm/drm_auth.h
new file mode 100644
index 000000000..50131383e
--- /dev/null
+++ b/include/drm/drm_auth.h
@@ -0,0 +1,139 @@
+#ifndef _DRM_AUTH_H_
+#define _DRM_AUTH_H_
+
+/*
+ * Internal Header for the Direct Rendering Manager
+ *
+ * Copyright 2016 Intel Corporation
+ *
+ * Author: Daniel Vetter <daniel.vetter@ffwll.ch>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <linux/idr.h>
+#include <linux/kref.h>
+#include <linux/wait.h>
+
+struct drm_file;
+
+/**
+ * struct drm_master - drm master structure
+ *
+ * @refcount: Refcount for this master object.
+ * @dev: Link back to the DRM device
+ * @driver_priv: Pointer to driver-private information.
+ *
+ * Note that master structures are only relevant for the legacy/primary device
+ * nodes, hence there can only be one per device, not one per drm_minor.
+ */
+struct drm_master {
+	struct kref refcount;
+	struct drm_device *dev;
+	/**
+	 * @unique: Unique identifier: e.g. busid. Protected by
+	 * &drm_device.master_mutex.
+	 */
+	char *unique;
+	/**
+	 * @unique_len: Length of unique field. Protected by
+	 * &drm_device.master_mutex.
+	 */
+	int unique_len;
+	/**
+	 * @magic_map: Map of used authentication tokens. Protected by
+	 * &drm_device.master_mutex.
+	 */
+	struct idr magic_map;
+	void *driver_priv;
+
+	/**
+	 * @lessor:
+	 *
+	 * Lease grantor, only set if this &struct drm_master represents a
+	 * lessee holding a lease of objects from @lessor. Full owners of the
+	 * device have this set to NULL.
+	 *
+	 * The lessor does not change once it's set in drm_lease_create(), and
+	 * each lessee holds a reference to its lessor that it releases upon
+	 * being destroyed in drm_lease_destroy().
+	 *
+	 * See also the :ref:`section on display resource leasing
+	 * <drm_leasing>`.
+	 */
+	struct drm_master *lessor;
+
+	/**
+	 * @lessee_id:
+	 *
+	 * ID for lessees. Owners (i.e. @lessor is NULL) always have ID 0.
+	 * Protected by &drm_device.mode_config's &drm_mode_config.idr_mutex.
+	 */
+	int	lessee_id;
+
+	/**
+	 * @lessee_list:
+	 *
+	 * List entry of lessees of @lessor, where they are linked to @lessees.
+	 * Not used for owners. Protected by &drm_device.mode_config's
+	 * &drm_mode_config.idr_mutex.
+	 */
+	struct list_head lessee_list;
+
+	/**
+	 * @lessees:
+	 *
+	 * List of drm_masters leasing from this one. Protected by
+	 * &drm_device.mode_config's &drm_mode_config.idr_mutex.
+	 *
+	 * This list is empty if no leases have been granted, or if all lessees
+	 * have been destroyed. Since lessors are referenced by all their
+	 * lessees, this master cannot be destroyed unless the list is empty.
+	 */
+	struct list_head lessees;
+
+	/**
+	 * @leases:
+	 *
+	 * Objects leased to this drm_master. Protected by
+	 * &drm_device.mode_config's &drm_mode_config.idr_mutex.
+	 *
+	 * Objects are leased all together in drm_lease_create(), and are
+	 * removed all together when the lease is revoked.
+	 */
+	struct idr leases;
+
+	/**
+	 * @lessee_idr:
+	 *
+	 * All lessees under this owner (only used where @lessor is NULL).
+	 * Protected by &drm_device.mode_config's &drm_mode_config.idr_mutex.
+	 */
+	struct idr lessee_idr;
+};
+
+struct drm_master *drm_master_get(struct drm_master *master);
+struct drm_master *drm_file_get_master(struct drm_file *file_priv);
+void drm_master_put(struct drm_master **master);
+bool drm_is_current_master(struct drm_file *fpriv);
+
+struct drm_master *drm_master_create(struct drm_device *dev);
+
+#endif