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, 32 insertions, 0 deletions

diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h
new file mode 100644
index 000000000..4092bf2ed
--- /dev/null
+++ b/arch/x86/boot/string.h
@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef BOOT_STRING_H
+#define BOOT_STRING_H
+
+/* Undef any of these macros coming from string_32.h. */
+#undef memcpy
+#undef memset
+#undef memcmp
+
+void *memcpy(void *dst, const void *src, size_t len);
+void *memmove(void *dst, const void *src, size_t len);
+void *memset(void *dst, int c, size_t len);
+int memcmp(const void *s1, const void *s2, size_t len);
+int bcmp(const void *s1, const void *s2, size_t len);
+
+/* Access builtin version by default. */
+#define memcpy(d,s,l) __builtin_memcpy(d,s,l)
+#define memset(d,c,l) __builtin_memset(d,c,l)
+#define memcmp	__builtin_memcmp
+
+extern int strcmp(const char *str1, const char *str2);
+extern int strncmp(const char *cs, const char *ct, size_t count);
+extern size_t strlen(const char *s);
+extern char *strstr(const char *s1, const char *s2);
+extern char *strchr(const char *s, int c);
+extern size_t strnlen(const char *s, size_t maxlen);
+extern unsigned long long simple_strtoull(const char *cp, char **endp,
+					  unsigned int base);
+long simple_strtol(const char *cp, char **endp, unsigned int base);
+
+int boot_kstrtoul(const char *s, unsigned int base, unsigned long *res);
+#endif /* BOOT_STRING_H */