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, 270 insertions, 0 deletions

diff --git a/include/net/lwtunnel.h b/include/net/lwtunnel.h
new file mode 100644
index 000000000..26232f603
--- /dev/null
+++ b/include/net/lwtunnel.h
@@ -0,0 +1,270 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_LWTUNNEL_H
+#define __NET_LWTUNNEL_H 1
+
+#include <linux/lwtunnel.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <linux/types.h>
+#include <net/route.h>
+
+#define LWTUNNEL_HASH_BITS   7
+#define LWTUNNEL_HASH_SIZE   (1 << LWTUNNEL_HASH_BITS)
+
+/* lw tunnel state flags */
+#define LWTUNNEL_STATE_OUTPUT_REDIRECT	BIT(0)
+#define LWTUNNEL_STATE_INPUT_REDIRECT	BIT(1)
+#define LWTUNNEL_STATE_XMIT_REDIRECT	BIT(2)
+
+/* LWTUNNEL_XMIT_CONTINUE should be distinguishable from dst_output return
+ * values (NET_XMIT_xxx and NETDEV_TX_xxx in linux/netdevice.h) for safety.
+ */
+enum {
+	LWTUNNEL_XMIT_DONE,
+	LWTUNNEL_XMIT_CONTINUE = 0x100,
+};
+
+
+struct lwtunnel_state {
+	__u16		type;
+	__u16		flags;
+	__u16		headroom;
+	atomic_t	refcnt;
+	int		(*orig_output)(struct net *net, struct sock *sk, struct sk_buff *skb);
+	int		(*orig_input)(struct sk_buff *);
+	struct		rcu_head rcu;
+	__u8            data[];
+};
+
+struct lwtunnel_encap_ops {
+	int (*build_state)(struct net *net, struct nlattr *encap,
+			   unsigned int family, const void *cfg,
+			   struct lwtunnel_state **ts,
+			   struct netlink_ext_ack *extack);
+	void (*destroy_state)(struct lwtunnel_state *lws);
+	int (*output)(struct net *net, struct sock *sk, struct sk_buff *skb);
+	int (*input)(struct sk_buff *skb);
+	int (*fill_encap)(struct sk_buff *skb,
+			  struct lwtunnel_state *lwtstate);
+	int (*get_encap_size)(struct lwtunnel_state *lwtstate);
+	int (*cmp_encap)(struct lwtunnel_state *a, struct lwtunnel_state *b);
+	int (*xmit)(struct sk_buff *skb);
+
+	struct module *owner;
+};
+
+#ifdef CONFIG_LWTUNNEL
+
+DECLARE_STATIC_KEY_FALSE(nf_hooks_lwtunnel_enabled);
+
+void lwtstate_free(struct lwtunnel_state *lws);
+
+static inline struct lwtunnel_state *
+lwtstate_get(struct lwtunnel_state *lws)
+{
+	if (lws)
+		atomic_inc(&lws->refcnt);
+
+	return lws;
+}
+
+static inline void lwtstate_put(struct lwtunnel_state *lws)
+{
+	if (!lws)
+		return;
+
+	if (atomic_dec_and_test(&lws->refcnt))
+		lwtstate_free(lws);
+}
+
+static inline bool lwtunnel_output_redirect(struct lwtunnel_state *lwtstate)
+{
+	if (lwtstate && (lwtstate->flags & LWTUNNEL_STATE_OUTPUT_REDIRECT))
+		return true;
+
+	return false;
+}
+
+static inline bool lwtunnel_input_redirect(struct lwtunnel_state *lwtstate)
+{
+	if (lwtstate && (lwtstate->flags & LWTUNNEL_STATE_INPUT_REDIRECT))
+		return true;
+
+	return false;
+}
+
+static inline bool lwtunnel_xmit_redirect(struct lwtunnel_state *lwtstate)
+{
+	if (lwtstate && (lwtstate->flags & LWTUNNEL_STATE_XMIT_REDIRECT))
+		return true;
+
+	return false;
+}
+
+static inline unsigned int lwtunnel_headroom(struct lwtunnel_state *lwtstate,
+					     unsigned int mtu)
+{
+	if ((lwtunnel_xmit_redirect(lwtstate) ||
+	     lwtunnel_output_redirect(lwtstate)) && lwtstate->headroom < mtu)
+		return lwtstate->headroom;
+
+	return 0;
+}
+
+int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *op,
+			   unsigned int num);
+int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *op,
+			   unsigned int num);
+int lwtunnel_valid_encap_type(u16 encap_type,
+			      struct netlink_ext_ack *extack);
+int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int len,
+				   struct netlink_ext_ack *extack);
+int lwtunnel_build_state(struct net *net, u16 encap_type,
+			 struct nlattr *encap,
+			 unsigned int family, const void *cfg,
+			 struct lwtunnel_state **lws,
+			 struct netlink_ext_ack *extack);
+int lwtunnel_fill_encap(struct sk_buff *skb, struct lwtunnel_state *lwtstate,
+			int encap_attr, int encap_type_attr);
+int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate);
+struct lwtunnel_state *lwtunnel_state_alloc(int hdr_len);
+int lwtunnel_cmp_encap(struct lwtunnel_state *a, struct lwtunnel_state *b);
+int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb);
+int lwtunnel_input(struct sk_buff *skb);
+int lwtunnel_xmit(struct sk_buff *skb);
+int bpf_lwt_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len,
+			  bool ingress);
+
+static inline void lwtunnel_set_redirect(struct dst_entry *dst)
+{
+	if (lwtunnel_output_redirect(dst->lwtstate)) {
+		dst->lwtstate->orig_output = READ_ONCE(dst->output);
+		WRITE_ONCE(dst->output, lwtunnel_output);
+	}
+	if (lwtunnel_input_redirect(dst->lwtstate)) {
+		dst->lwtstate->orig_input = READ_ONCE(dst->input);
+		WRITE_ONCE(dst->input, lwtunnel_input);
+	}
+}
+#else
+
+static inline void lwtstate_free(struct lwtunnel_state *lws)
+{
+}
+
+static inline struct lwtunnel_state *
+lwtstate_get(struct lwtunnel_state *lws)
+{
+	return lws;
+}
+
+static inline void lwtstate_put(struct lwtunnel_state *lws)
+{
+}
+
+static inline bool lwtunnel_output_redirect(struct lwtunnel_state *lwtstate)
+{
+	return false;
+}
+
+static inline bool lwtunnel_input_redirect(struct lwtunnel_state *lwtstate)
+{
+	return false;
+}
+
+static inline bool lwtunnel_xmit_redirect(struct lwtunnel_state *lwtstate)
+{
+	return false;
+}
+
+static inline void lwtunnel_set_redirect(struct dst_entry *dst)
+{
+}
+
+static inline unsigned int lwtunnel_headroom(struct lwtunnel_state *lwtstate,
+					     unsigned int mtu)
+{
+	return 0;
+}
+
+static inline int lwtunnel_encap_add_ops(const struct lwtunnel_encap_ops *op,
+					 unsigned int num)
+{
+	return -EOPNOTSUPP;
+
+}
+
+static inline int lwtunnel_encap_del_ops(const struct lwtunnel_encap_ops *op,
+					 unsigned int num)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_valid_encap_type(u16 encap_type,
+					    struct netlink_ext_ack *extack)
+{
+	NL_SET_ERR_MSG(extack, "CONFIG_LWTUNNEL is not enabled in this kernel");
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_valid_encap_type_attr(struct nlattr *attr, int len,
+						 struct netlink_ext_ack *extack)
+{
+	/* return 0 since we are not walking attr looking for
+	 * RTA_ENCAP_TYPE attribute on nexthops.
+	 */
+	return 0;
+}
+
+static inline int lwtunnel_build_state(struct net *net, u16 encap_type,
+				       struct nlattr *encap,
+				       unsigned int family, const void *cfg,
+				       struct lwtunnel_state **lws,
+				       struct netlink_ext_ack *extack)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_fill_encap(struct sk_buff *skb,
+				      struct lwtunnel_state *lwtstate,
+				      int encap_attr, int encap_type_attr)
+{
+	return 0;
+}
+
+static inline int lwtunnel_get_encap_size(struct lwtunnel_state *lwtstate)
+{
+	return 0;
+}
+
+static inline struct lwtunnel_state *lwtunnel_state_alloc(int hdr_len)
+{
+	return NULL;
+}
+
+static inline int lwtunnel_cmp_encap(struct lwtunnel_state *a,
+				     struct lwtunnel_state *b)
+{
+	return 0;
+}
+
+static inline int lwtunnel_output(struct net *net, struct sock *sk, struct sk_buff *skb)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_input(struct sk_buff *skb)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline int lwtunnel_xmit(struct sk_buff *skb)
+{
+	return -EOPNOTSUPP;
+}
+
+#endif /* CONFIG_LWTUNNEL */
+
+#define MODULE_ALIAS_RTNL_LWT(encap_type) MODULE_ALIAS("rtnl-lwt-" __stringify(encap_type))
+
+#endif /* __NET_LWTUNNEL_H */