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, 40 insertions, 0 deletions

diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
new file mode 100644
index 000000000..654d37ec0
--- /dev/null
+++ b/include/net/sctp/checksum.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* SCTP kernel reference Implementation
+ * Copyright (c) 1999-2001 Motorola, Inc.
+ * Copyright (c) 2001-2003 International Business Machines, Corp.
+ *
+ * This file is part of the SCTP kernel reference Implementation
+ *
+ * SCTP Checksum functions
+ *
+ * Please send any bug reports or fixes you make to the
+ * email address(es):
+ *    lksctp developers <linux-sctp@vger.kernel.org>
+ *
+ * Written or modified by:
+ *    Dinakaran Joseph
+ *    Jon Grimm <jgrimm@us.ibm.com>
+ *    Sridhar Samudrala <sri@us.ibm.com>
+ *    Vlad Yasevich <vladislav.yasevich@hp.com>
+ */
+
+#ifndef __sctp_checksum_h__
+#define __sctp_checksum_h__
+
+#include <linux/types.h>
+#include <linux/sctp.h>
+
+static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
+					unsigned int offset)
+{
+	struct sctphdr *sh = (struct sctphdr *)(skb->data + offset);
+	__le32 old = sh->checksum;
+	u32 new;
+
+	sh->checksum = 0;
+	new = ~skb_crc32c(skb, offset, skb->len - offset, ~0);
+	sh->checksum = old;
+	return cpu_to_le32(new);
+}
+
+#endif /* __sctp_checksum_h__ */