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, 88 insertions, 0 deletions

diff --git a/net/nfc/af_nfc.c b/net/nfc/af_nfc.c
new file mode 100644
index 000000000..dda323e0a
--- /dev/null
+++ b/net/nfc/af_nfc.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2011 Instituto Nokia de Tecnologia
+ *
+ * Authors:
+ *    Aloisio Almeida Jr <aloisio.almeida@openbossa.org>
+ *    Lauro Ramos Venancio <lauro.venancio@openbossa.org>
+ */
+
+#include <linux/nfc.h>
+#include <linux/module.h>
+
+#include "nfc.h"
+
+static DEFINE_RWLOCK(proto_tab_lock);
+static const struct nfc_protocol *proto_tab[NFC_SOCKPROTO_MAX];
+
+static int nfc_sock_create(struct net *net, struct socket *sock, int proto,
+			   int kern)
+{
+	int rc = -EPROTONOSUPPORT;
+
+	if (net != &init_net)
+		return -EAFNOSUPPORT;
+
+	if (proto < 0 || proto >= NFC_SOCKPROTO_MAX)
+		return -EINVAL;
+
+	read_lock(&proto_tab_lock);
+	if (proto_tab[proto] &&	try_module_get(proto_tab[proto]->owner)) {
+		rc = proto_tab[proto]->create(net, sock, proto_tab[proto], kern);
+		module_put(proto_tab[proto]->owner);
+	}
+	read_unlock(&proto_tab_lock);
+
+	return rc;
+}
+
+static const struct net_proto_family nfc_sock_family_ops = {
+	.owner  = THIS_MODULE,
+	.family = PF_NFC,
+	.create = nfc_sock_create,
+};
+
+int nfc_proto_register(const struct nfc_protocol *nfc_proto)
+{
+	int rc;
+
+	if (nfc_proto->id < 0 || nfc_proto->id >= NFC_SOCKPROTO_MAX)
+		return -EINVAL;
+
+	rc = proto_register(nfc_proto->proto, 0);
+	if (rc)
+		return rc;
+
+	write_lock(&proto_tab_lock);
+	if (proto_tab[nfc_proto->id])
+		rc = -EBUSY;
+	else
+		proto_tab[nfc_proto->id] = nfc_proto;
+	write_unlock(&proto_tab_lock);
+
+	if (rc)
+		proto_unregister(nfc_proto->proto);
+
+	return rc;
+}
+EXPORT_SYMBOL(nfc_proto_register);
+
+void nfc_proto_unregister(const struct nfc_protocol *nfc_proto)
+{
+	write_lock(&proto_tab_lock);
+	proto_tab[nfc_proto->id] = NULL;
+	write_unlock(&proto_tab_lock);
+
+	proto_unregister(nfc_proto->proto);
+}
+EXPORT_SYMBOL(nfc_proto_unregister);
+
+int __init af_nfc_init(void)
+{
+	return sock_register(&nfc_sock_family_ops);
+}
+
+void __exit af_nfc_exit(void)
+{
+	sock_unregister(PF_NFC);
+}