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, 75 insertions, 0 deletions

diff --git a/net/mctp/test/utils.h b/net/mctp/test/utils.h
new file mode 100644
index 000000000..47603732e
--- /dev/null
+++ b/net/mctp/test/utils.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __NET_MCTP_TEST_UTILS_H
+#define __NET_MCTP_TEST_UTILS_H
+
+#include <uapi/linux/netdevice.h>
+
+#include <net/mctp.h>
+#include <net/mctpdevice.h>
+
+#include <kunit/test.h>
+
+#define MCTP_DEV_TEST_MTU	68
+
+struct mctp_test_dev {
+	struct net_device *ndev;
+	struct mctp_dev *mdev;
+
+	unsigned short lladdr_len;
+	unsigned char lladdr[MAX_ADDR_LEN];
+
+	struct sk_buff_head pkts;
+};
+
+struct mctp_test_dev;
+
+struct mctp_test_route {
+	struct mctp_route	rt;
+};
+
+struct mctp_test_bind_setup {
+	mctp_eid_t bind_addr;
+	int bind_net;
+	u8 bind_type;
+
+	bool have_peer;
+	mctp_eid_t peer_addr;
+	int peer_net;
+
+	/* optional name. Used for comparison in "lookup" tests */
+	const char *name;
+};
+
+struct mctp_test_dev *mctp_test_create_dev(void);
+struct mctp_test_dev *mctp_test_create_dev_with_addr(mctp_eid_t eid);
+struct mctp_test_dev *mctp_test_create_dev_lladdr(unsigned short lladdr_len,
+						  const unsigned char *lladdr);
+void mctp_test_destroy_dev(struct mctp_test_dev *dev);
+
+struct mctp_test_route *mctp_test_create_route_direct(struct net *net,
+						      struct mctp_dev *dev,
+						      mctp_eid_t eid,
+						      unsigned int mtu);
+struct mctp_test_route *mctp_test_create_route_gw(struct net *net,
+						  unsigned int netid,
+						  mctp_eid_t eid,
+						  mctp_eid_t gw,
+						  unsigned int mtu);
+void mctp_test_dst_setup(struct kunit *test, struct mctp_dst *dst,
+			 struct mctp_test_dev *dev, unsigned int mtu);
+void mctp_test_route_destroy(struct kunit *test, struct mctp_test_route *rt);
+void mctp_test_skb_set_dev(struct sk_buff *skb, struct mctp_test_dev *dev);
+struct sk_buff *mctp_test_create_skb(const struct mctp_hdr *hdr,
+				     unsigned int data_len);
+struct sk_buff *__mctp_test_create_skb_data(const struct mctp_hdr *hdr,
+					    const void *data, size_t data_len);
+
+#define mctp_test_create_skb_data(h, d) \
+	__mctp_test_create_skb_data(h, d, sizeof(*d))
+
+void mctp_test_bind_run(struct kunit *test,
+			const struct mctp_test_bind_setup *setup,
+			int *ret_bind_errno, struct socket **sock);
+
+#endif /* __NET_MCTP_TEST_UTILS_H */