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, 64 insertions, 0 deletions

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
new file mode 100644
index 000000000..2dba7f83e
--- /dev/null
+++ b/arch/x86/lib/Makefile
@@ -0,0 +1,64 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for x86 specific library files.
+#
+
+# Produces uninteresting flaky coverage.
+KCOV_INSTRUMENT_delay.o	:= n
+
+# KCSAN uses udelay for introducing watchpoint delay; avoid recursion.
+KCSAN_SANITIZE_delay.o := n
+ifdef CONFIG_KCSAN
+# In case KCSAN+lockdep+ftrace are enabled, disable ftrace for delay.o to avoid
+# lockdep -> [other libs] -> KCSAN -> udelay -> ftrace -> lockdep recursion.
+CFLAGS_REMOVE_delay.o = $(CC_FLAGS_FTRACE)
+endif
+
+inat_tables_script = $(srctree)/arch/x86/tools/gen-insn-attr-x86.awk
+inat_tables_maps = $(srctree)/arch/x86/lib/x86-opcode-map.txt
+quiet_cmd_inat_tables = GEN     $@
+      cmd_inat_tables = $(AWK) -f $(inat_tables_script) $(inat_tables_maps) > $@
+
+$(obj)/inat-tables.c: $(inat_tables_script) $(inat_tables_maps)
+	$(call cmd,inat_tables)
+
+$(obj)/inat.o: $(obj)/inat-tables.c
+
+clean-files := inat-tables.c
+
+obj-$(CONFIG_SMP) += msr-smp.o cache-smp.o
+
+lib-y := delay.o misc.o cmdline.o cpu.o
+lib-y += usercopy_$(BITS).o usercopy.o getuser.o putuser.o
+lib-y += memcpy_$(BITS).o
+lib-y += pc-conf-reg.o
+lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_mc.o copy_mc_64.o
+lib-$(CONFIG_INSTRUCTION_DECODER) += insn.o inat.o insn-eval.o
+lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
+lib-$(CONFIG_FUNCTION_ERROR_INJECTION)	+= error-inject.o
+lib-$(CONFIG_MITIGATION_RETPOLINE) += retpoline.o
+
+obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
+obj-y += iomem.o
+
+ifeq ($(CONFIG_X86_32),y)
+        obj-y += atomic64_32.o
+        lib-y += atomic64_cx8_32.o
+        lib-y += checksum_32.o
+        lib-y += strstr_32.o
+        lib-y += string_32.o
+        lib-y += memmove_32.o
+        lib-y += cmpxchg8b_emu.o
+ifneq ($(CONFIG_X86_CX8),y)
+        lib-y += atomic64_386_32.o
+endif
+else
+ifneq ($(CONFIG_GENERIC_CSUM),y)
+        lib-y += csum-partial_64.o csum-copy_64.o csum-wrappers_64.o
+endif
+        lib-y += clear_page_64.o copy_page_64.o
+        lib-y += memmove_64.o memset_64.o
+        lib-y += copy_user_64.o copy_user_uncached_64.o
+        lib-y += cmpxchg16b_emu.o
+        lib-y += bhi.o
+endif