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, 240 insertions, 0 deletions

diff --git a/lib/test_static_keys.c b/lib/test_static_keys.c
new file mode 100644
index 000000000..00c715f30
--- /dev/null
+++ b/lib/test_static_keys.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Kernel module for testing static keys.
+ *
+ * Copyright 2015 Akamai Technologies Inc. All Rights Reserved
+ *
+ * Authors:
+ *      Jason Baron       <jbaron@akamai.com>
+ */
+
+#include <linux/module.h>
+#include <linux/jump_label.h>
+
+/* old keys */
+struct static_key old_true_key	= STATIC_KEY_INIT_TRUE;
+struct static_key old_false_key	= STATIC_KEY_INIT_FALSE;
+
+/* new api */
+DEFINE_STATIC_KEY_TRUE(true_key);
+DEFINE_STATIC_KEY_FALSE(false_key);
+
+/* external */
+extern struct static_key base_old_true_key;
+extern struct static_key base_inv_old_true_key;
+extern struct static_key base_old_false_key;
+extern struct static_key base_inv_old_false_key;
+
+/* new api */
+extern struct static_key_true base_true_key;
+extern struct static_key_true base_inv_true_key;
+extern struct static_key_false base_false_key;
+extern struct static_key_false base_inv_false_key;
+
+
+struct test_key {
+	bool			init_state;
+	struct static_key	*key;
+	bool			(*test_key)(void);
+};
+
+#define test_key_func(key, branch)	\
+static bool key ## _ ## branch(void)	\
+{					\
+	return branch(&key);		\
+}
+
+static void invert_key(struct static_key *key)
+{
+	if (static_key_enabled(key))
+		static_key_disable(key);
+	else
+		static_key_enable(key);
+}
+
+static void invert_keys(struct test_key *keys, int size)
+{
+	struct static_key *previous = NULL;
+	int i;
+
+	for (i = 0; i < size; i++) {
+		if (previous != keys[i].key) {
+			invert_key(keys[i].key);
+			previous = keys[i].key;
+		}
+	}
+}
+
+static int verify_keys(struct test_key *keys, int size, bool invert)
+{
+	int i;
+	bool ret, init;
+
+	for (i = 0; i < size; i++) {
+		ret = static_key_enabled(keys[i].key);
+		init = keys[i].init_state;
+		if (ret != (invert ? !init : init))
+			return -EINVAL;
+		ret = keys[i].test_key();
+		if (static_key_enabled(keys[i].key)) {
+			if (!ret)
+				return -EINVAL;
+		} else {
+			if (ret)
+				return -EINVAL;
+		}
+	}
+	return 0;
+}
+
+test_key_func(old_true_key, static_key_true)
+test_key_func(old_false_key, static_key_false)
+test_key_func(true_key, static_branch_likely)
+test_key_func(true_key, static_branch_unlikely)
+test_key_func(false_key, static_branch_likely)
+test_key_func(false_key, static_branch_unlikely)
+test_key_func(base_old_true_key, static_key_true)
+test_key_func(base_inv_old_true_key, static_key_true)
+test_key_func(base_old_false_key, static_key_false)
+test_key_func(base_inv_old_false_key, static_key_false)
+test_key_func(base_true_key, static_branch_likely)
+test_key_func(base_true_key, static_branch_unlikely)
+test_key_func(base_inv_true_key, static_branch_likely)
+test_key_func(base_inv_true_key, static_branch_unlikely)
+test_key_func(base_false_key, static_branch_likely)
+test_key_func(base_false_key, static_branch_unlikely)
+test_key_func(base_inv_false_key, static_branch_likely)
+test_key_func(base_inv_false_key, static_branch_unlikely)
+
+static int __init test_static_key_init(void)
+{
+	int ret;
+	int size;
+
+	struct test_key static_key_tests[] = {
+		/* internal keys - old keys */
+		{
+			.init_state	= true,
+			.key		= &old_true_key,
+			.test_key	= &old_true_key_static_key_true,
+		},
+		{
+			.init_state	= false,
+			.key		= &old_false_key,
+			.test_key	= &old_false_key_static_key_false,
+		},
+		/* internal keys - new keys */
+		{
+			.init_state	= true,
+			.key		= &true_key.key,
+			.test_key	= &true_key_static_branch_likely,
+		},
+		{
+			.init_state	= true,
+			.key		= &true_key.key,
+			.test_key	= &true_key_static_branch_unlikely,
+		},
+		{
+			.init_state	= false,
+			.key		= &false_key.key,
+			.test_key	= &false_key_static_branch_likely,
+		},
+		{
+			.init_state	= false,
+			.key		= &false_key.key,
+			.test_key	= &false_key_static_branch_unlikely,
+		},
+		/* external keys - old keys */
+		{
+			.init_state	= true,
+			.key		= &base_old_true_key,
+			.test_key	= &base_old_true_key_static_key_true,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_inv_old_true_key,
+			.test_key	= &base_inv_old_true_key_static_key_true,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_old_false_key,
+			.test_key	= &base_old_false_key_static_key_false,
+		},
+		{
+			.init_state	= true,
+			.key		= &base_inv_old_false_key,
+			.test_key	= &base_inv_old_false_key_static_key_false,
+		},
+		/* external keys - new keys */
+		{
+			.init_state	= true,
+			.key		= &base_true_key.key,
+			.test_key	= &base_true_key_static_branch_likely,
+		},
+		{
+			.init_state	= true,
+			.key		= &base_true_key.key,
+			.test_key	= &base_true_key_static_branch_unlikely,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_inv_true_key.key,
+			.test_key	= &base_inv_true_key_static_branch_likely,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_inv_true_key.key,
+			.test_key	= &base_inv_true_key_static_branch_unlikely,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_false_key.key,
+			.test_key	= &base_false_key_static_branch_likely,
+		},
+		{
+			.init_state	= false,
+			.key		= &base_false_key.key,
+			.test_key	= &base_false_key_static_branch_unlikely,
+		},
+		{
+			.init_state	= true,
+			.key		= &base_inv_false_key.key,
+			.test_key	= &base_inv_false_key_static_branch_likely,
+		},
+		{
+			.init_state	= true,
+			.key		= &base_inv_false_key.key,
+			.test_key	= &base_inv_false_key_static_branch_unlikely,
+		},
+	};
+
+	size = ARRAY_SIZE(static_key_tests);
+
+	ret = verify_keys(static_key_tests, size, false);
+	if (ret)
+		goto out;
+
+	invert_keys(static_key_tests, size);
+	ret = verify_keys(static_key_tests, size, true);
+	if (ret)
+		goto out;
+
+	invert_keys(static_key_tests, size);
+	ret = verify_keys(static_key_tests, size, false);
+	if (ret)
+		goto out;
+	return 0;
+out:
+	return ret;
+}
+
+static void __exit test_static_key_exit(void)
+{
+}
+
+module_init(test_static_key_init);
+module_exit(test_static_key_exit);
+
+MODULE_AUTHOR("Jason Baron <jbaron@akamai.com>");
+MODULE_DESCRIPTION("Kernel module for testing static keys");
+MODULE_LICENSE("GPL");