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

2 files changed, 105 insertions, 0 deletions

diff --git a/samples/kmemleak/Makefile b/samples/kmemleak/Makefile
new file mode 100644
index 000000000..8a999ab43
--- /dev/null
+++ b/samples/kmemleak/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-$(CONFIG_SAMPLE_KMEMLEAK) += kmemleak-test.o
diff --git a/samples/kmemleak/kmemleak-test.c b/samples/kmemleak/kmemleak-test.c
new file mode 100644
index 000000000..8609812a3
--- /dev/null
+++ b/samples/kmemleak/kmemleak-test.c
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * samples/kmemleak/kmemleak-test.c
+ *
+ * Copyright (C) 2008 ARM Limited
+ * Written by Catalin Marinas <catalin.marinas@arm.com>
+ */
+
+#define pr_fmt(fmt) "kmemleak: " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/list.h>
+#include <linux/percpu.h>
+#include <linux/fdtable.h>
+
+#include <linux/kmemleak.h>
+
+struct test_node {
+	long header[25];
+	struct list_head list;
+	long footer[25];
+};
+
+static LIST_HEAD(test_list);
+static DEFINE_PER_CPU(void *, kmemleak_test_pointer);
+
+/*
+ * Some very simple testing. This function needs to be extended for
+ * proper testing.
+ */
+static int kmemleak_test_init(void)
+{
+	struct test_node *elem;
+	int i;
+
+	pr_info("Kmemleak testing\n");
+
+	/* make some orphan objects */
+	pr_info("kmalloc(32) = 0x%px\n", kmalloc(32, GFP_KERNEL));
+	pr_info("kmalloc(32) = 0x%px\n", kmalloc(32, GFP_KERNEL));
+	pr_info("kmalloc(1024) = 0x%px\n", kmalloc(1024, GFP_KERNEL));
+	pr_info("kmalloc(1024) = 0x%px\n", kmalloc(1024, GFP_KERNEL));
+	pr_info("kmalloc(2048) = 0x%px\n", kmalloc(2048, GFP_KERNEL));
+	pr_info("kmalloc(2048) = 0x%px\n", kmalloc(2048, GFP_KERNEL));
+	pr_info("kmalloc(4096) = 0x%px\n", kmalloc(4096, GFP_KERNEL));
+	pr_info("kmalloc(4096) = 0x%px\n", kmalloc(4096, GFP_KERNEL));
+#ifndef CONFIG_MODULES
+	pr_info("kmem_cache_alloc(files_cachep) = 0x%px\n",
+		kmem_cache_alloc(files_cachep, GFP_KERNEL));
+	pr_info("kmem_cache_alloc(files_cachep) = 0x%px\n",
+		kmem_cache_alloc(files_cachep, GFP_KERNEL));
+#endif
+	pr_info("vmalloc(64) = 0x%px\n", vmalloc(64));
+	pr_info("vmalloc(64) = 0x%px\n", vmalloc(64));
+	pr_info("vmalloc(64) = 0x%px\n", vmalloc(64));
+	pr_info("vmalloc(64) = 0x%px\n", vmalloc(64));
+	pr_info("vmalloc(64) = 0x%px\n", vmalloc(64));
+
+	/*
+	 * Add elements to a list. They should only appear as orphan
+	 * after the module is removed.
+	 */
+	for (i = 0; i < 10; i++) {
+		elem = kzalloc(sizeof(*elem), GFP_KERNEL);
+		pr_info("kzalloc(sizeof(*elem)) = 0x%px\n", elem);
+		if (!elem)
+			return -ENOMEM;
+		INIT_LIST_HEAD(&elem->list);
+		list_add_tail(&elem->list, &test_list);
+	}
+
+	for_each_possible_cpu(i) {
+		per_cpu(kmemleak_test_pointer, i) = kmalloc(129, GFP_KERNEL);
+		pr_info("kmalloc(129) = 0x%px\n",
+			per_cpu(kmemleak_test_pointer, i));
+	}
+
+	pr_info("__alloc_percpu(64, 4) = 0x%px\n", __alloc_percpu(64, 4));
+
+	return 0;
+}
+module_init(kmemleak_test_init);
+
+static void __exit kmemleak_test_exit(void)
+{
+	struct test_node *elem, *tmp;
+
+	/*
+	 * Remove the list elements without actually freeing the
+	 * memory.
+	 */
+	list_for_each_entry_safe(elem, tmp, &test_list, list)
+		list_del(&elem->list);
+}
+module_exit(kmemleak_test_exit);
+
+MODULE_DESCRIPTION("Sample module to leak memory for kmemleak testing");
+MODULE_LICENSE("GPL");