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, 159 insertions, 0 deletions

diff --git a/include/net/llc.h b/include/net/llc.h
new file mode 100644
index 000000000..029ba8a22
--- /dev/null
+++ b/include/net/llc.h
@@ -0,0 +1,159 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LLC_H
+#define LLC_H
+/*
+ * Copyright (c) 1997 by Procom Technology, Inc.
+ * 		 2001-2003 by Arnaldo Carvalho de Melo <acme@conectiva.com.br>
+ */
+
+#include <linux/if.h>
+#include <linux/if_ether.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/rculist_nulls.h>
+#include <linux/hash.h>
+#include <linux/jhash.h>
+
+#include <linux/atomic.h>
+
+struct net_device;
+struct packet_type;
+struct sk_buff;
+
+struct llc_addr {
+	unsigned char lsap;
+	unsigned char mac[IFHWADDRLEN];
+};
+
+#define LLC_SAP_STATE_INACTIVE	1
+#define LLC_SAP_STATE_ACTIVE	2
+
+#define LLC_SK_DEV_HASH_BITS 6
+#define LLC_SK_DEV_HASH_ENTRIES (1<<LLC_SK_DEV_HASH_BITS)
+
+#define LLC_SK_LADDR_HASH_BITS 6
+#define LLC_SK_LADDR_HASH_ENTRIES (1<<LLC_SK_LADDR_HASH_BITS)
+
+/**
+ * struct llc_sap - Defines the SAP component
+ *
+ * @station - station this sap belongs to
+ * @state - sap state
+ * @p_bit - only lowest-order bit used
+ * @f_bit - only lowest-order bit used
+ * @laddr - SAP value in this 'lsap'
+ * @node - entry in station sap_list
+ * @sk_list - LLC sockets this one manages
+ */
+struct llc_sap {
+	unsigned char	 state;
+	unsigned char	 p_bit;
+	unsigned char	 f_bit;
+	refcount_t		 refcnt;
+	int		 (*rcv_func)(struct sk_buff *skb,
+				     struct net_device *dev,
+				     struct packet_type *pt,
+				     struct net_device *orig_dev);
+	struct llc_addr	 laddr;
+	struct list_head node;
+	spinlock_t sk_lock;
+	int sk_count;
+	struct hlist_nulls_head sk_laddr_hash[LLC_SK_LADDR_HASH_ENTRIES];
+	struct hlist_head sk_dev_hash[LLC_SK_DEV_HASH_ENTRIES];
+	struct rcu_head rcu;
+};
+
+static inline
+struct hlist_head *llc_sk_dev_hash(struct llc_sap *sap, int ifindex)
+{
+	u32 bucket = hash_32(ifindex, LLC_SK_DEV_HASH_BITS);
+
+	return &sap->sk_dev_hash[bucket];
+}
+
+static inline
+u32 llc_sk_laddr_hashfn(struct llc_sap *sap, const struct llc_addr *laddr)
+{
+	return hash_32(jhash(laddr->mac, sizeof(laddr->mac), 0),
+		       LLC_SK_LADDR_HASH_BITS);
+}
+
+static inline
+struct hlist_nulls_head *llc_sk_laddr_hash(struct llc_sap *sap,
+					   const struct llc_addr *laddr)
+{
+	return &sap->sk_laddr_hash[llc_sk_laddr_hashfn(sap, laddr)];
+}
+
+#define LLC_DEST_INVALID         0      /* Invalid LLC PDU type */
+#define LLC_DEST_SAP             1      /* Type 1 goes here */
+#define LLC_DEST_CONN            2      /* Type 2 goes here */
+
+extern struct list_head llc_sap_list;
+
+int llc_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
+	    struct net_device *orig_dev);
+
+int llc_mac_hdr_init(struct sk_buff *skb, const unsigned char *sa,
+		     const unsigned char *da);
+
+void llc_add_pack(int type,
+		  void (*handler)(struct llc_sap *sap, struct sk_buff *skb));
+void llc_remove_pack(int type);
+
+void llc_set_station_handler(void (*handler)(struct sk_buff *skb));
+
+struct llc_sap *llc_sap_open(unsigned char lsap,
+			     int (*rcv)(struct sk_buff *skb,
+					struct net_device *dev,
+					struct packet_type *pt,
+					struct net_device *orig_dev));
+static inline void llc_sap_hold(struct llc_sap *sap)
+{
+	refcount_inc(&sap->refcnt);
+}
+
+static inline bool llc_sap_hold_safe(struct llc_sap *sap)
+{
+	return refcount_inc_not_zero(&sap->refcnt);
+}
+
+void llc_sap_close(struct llc_sap *sap);
+
+static inline void llc_sap_put(struct llc_sap *sap)
+{
+	if (refcount_dec_and_test(&sap->refcnt))
+		llc_sap_close(sap);
+}
+
+struct llc_sap *llc_sap_find(unsigned char sap_value);
+
+int llc_build_and_send_ui_pkt(struct llc_sap *sap, struct sk_buff *skb,
+			      const unsigned char *dmac, unsigned char dsap);
+
+void llc_sap_handler(struct llc_sap *sap, struct sk_buff *skb);
+void llc_conn_handler(struct llc_sap *sap, struct sk_buff *skb);
+
+void llc_station_init(void);
+void llc_station_exit(void);
+
+#ifdef CONFIG_PROC_FS
+int llc_proc_init(void);
+void llc_proc_exit(void);
+#else
+#define llc_proc_init()	(0)
+#define llc_proc_exit()	do { } while(0)
+#endif /* CONFIG_PROC_FS */
+#ifdef CONFIG_SYSCTL
+int llc_sysctl_init(void);
+void llc_sysctl_exit(void);
+
+extern int sysctl_llc2_ack_timeout;
+extern int sysctl_llc2_busy_timeout;
+extern int sysctl_llc2_p_timeout;
+extern int sysctl_llc2_rej_timeout;
+#else
+#define llc_sysctl_init() (0)
+#define llc_sysctl_exit() do { } while(0)
+#endif /* CONFIG_SYSCTL */
+#endif /* LLC_H */