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, 79 insertions, 0 deletions

diff --git a/drivers/scsi/arm/msgqueue.h b/drivers/scsi/arm/msgqueue.h
new file mode 100644
index 000000000..4bcc400f5
--- /dev/null
+++ b/drivers/scsi/arm/msgqueue.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/drivers/acorn/scsi/msgqueue.h
+ *
+ *  Copyright (C) 1997 Russell King
+ *
+ *  message queue handling
+ */
+#ifndef MSGQUEUE_H
+#define MSGQUEUE_H
+
+struct message {
+    char msg[8];
+    int length;
+    int fifo;
+};
+
+struct msgqueue_entry {
+    struct message msg;
+    struct msgqueue_entry *next;
+};
+
+#define NR_MESSAGES 4
+
+typedef struct {
+    struct msgqueue_entry *qe;
+    struct msgqueue_entry *free;
+    struct msgqueue_entry entries[NR_MESSAGES];
+} MsgQueue_t;
+
+/*
+ * Function: void msgqueue_initialise(MsgQueue_t *msgq)
+ * Purpose : initialise a message queue
+ * Params  : msgq - queue to initialise
+ */
+extern void msgqueue_initialise(MsgQueue_t *msgq);
+
+/*
+ * Function: void msgqueue_free(MsgQueue_t *msgq)
+ * Purpose : free a queue
+ * Params  : msgq - queue to free
+ */
+extern void msgqueue_free(MsgQueue_t *msgq);
+
+/*
+ * Function: int msgqueue_msglength(MsgQueue_t *msgq)
+ * Purpose : calculate the total length of all messages on the message queue
+ * Params  : msgq - queue to examine
+ * Returns : number of bytes of messages in queue
+ */
+extern int msgqueue_msglength(MsgQueue_t *msgq);
+
+/*
+ * Function: struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno)
+ * Purpose : return a message & its length
+ * Params  : msgq   - queue to obtain message from
+ *         : msgno  - message number
+ * Returns : pointer to message string, or NULL
+ */
+extern struct message *msgqueue_getmsg(MsgQueue_t *msgq, int msgno);
+
+/*
+ * Function: int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...)
+ * Purpose : add a message onto a message queue
+ * Params  : msgq   - queue to add message on
+ *	     length - length of message
+ *	     ...    - message bytes
+ * Returns : != 0 if successful
+ */
+extern int msgqueue_addmsg(MsgQueue_t *msgq, int length, ...);
+
+/*
+ * Function: void msgqueue_flush(MsgQueue_t *msgq)
+ * Purpose : flush all messages from message queue
+ * Params  : msgq - queue to flush
+ */
+extern void msgqueue_flush(MsgQueue_t *msgq);
+
+#endif