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, 85 insertions, 0 deletions

diff --git a/include/net/ip6_checksum.h b/include/net/ip6_checksum.h
new file mode 100644
index 000000000..6677b3cc3
--- /dev/null
+++ b/include/net/ip6_checksum.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * INET		An implementation of the TCP/IP protocol suite for the LINUX
+ *		operating system.  INET is implemented using the  BSD Socket
+ *		interface as the means of communication with the user level.
+ *
+ *		Checksumming functions for IPv6
+ *
+ * Authors:	Jorge Cwik, <jorge@laser.satlink.net>
+ *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
+ *		Borrows very liberally from tcp.c and ip.c, see those
+ *		files for more names.
+ */
+
+/*
+ *	Fixes:
+ *
+ *	Ralf Baechle			:	generic ipv6 checksum
+ *	<ralf@waldorf-gmbh.de>
+ */
+
+#ifndef _CHECKSUM_IPV6_H
+#define _CHECKSUM_IPV6_H
+
+#include <asm/types.h>
+#include <asm/byteorder.h>
+#include <net/ip.h>
+#include <asm/checksum.h>
+#include <linux/in6.h>
+#include <linux/tcp.h>
+#include <linux/ipv6.h>
+
+#ifndef _HAVE_ARCH_IPV6_CSUM
+__sum16 csum_ipv6_magic(const struct in6_addr *saddr,
+			const struct in6_addr *daddr,
+			__u32 len, __u8 proto, __wsum csum);
+#endif
+
+static inline __wsum ip6_compute_pseudo(struct sk_buff *skb, int proto)
+{
+	return ~csum_unfold(csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
+					    &ipv6_hdr(skb)->daddr,
+					    skb->len, proto, 0));
+}
+
+static __inline__ __sum16 tcp_v6_check(int len,
+				   const struct in6_addr *saddr,
+				   const struct in6_addr *daddr,
+				   __wsum base)
+{
+	return csum_ipv6_magic(saddr, daddr, len, IPPROTO_TCP, base);
+}
+
+static inline void __tcp_v6_send_check(struct sk_buff *skb,
+				       const struct in6_addr *saddr,
+				       const struct in6_addr *daddr)
+{
+	struct tcphdr *th = tcp_hdr(skb);
+
+	th->check = ~tcp_v6_check(skb->len, saddr, daddr, 0);
+	skb->csum_start = skb_transport_header(skb) - skb->head;
+	skb->csum_offset = offsetof(struct tcphdr, check);
+}
+
+static inline void tcp_v6_gso_csum_prep(struct sk_buff *skb)
+{
+	struct ipv6hdr *ipv6h = ipv6_hdr(skb);
+	struct tcphdr *th = tcp_hdr(skb);
+
+	ipv6h->payload_len = 0;
+	th->check = ~tcp_v6_check(0, &ipv6h->saddr, &ipv6h->daddr, 0);
+}
+
+static inline __sum16 udp_v6_check(int len,
+				   const struct in6_addr *saddr,
+				   const struct in6_addr *daddr,
+				   __wsum base)
+{
+	return csum_ipv6_magic(saddr, daddr, len, IPPROTO_UDP, base);
+}
+
+void udp6_set_csum(bool nocheck, struct sk_buff *skb,
+		   const struct in6_addr *saddr,
+		   const struct in6_addr *daddr, int len);
+#endif