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, 98 insertions, 0 deletions

diff --git a/scripts/Makefile.vmlinux_o b/scripts/Makefile.vmlinux_o
new file mode 100644
index 000000000..24a3a4fd2
--- /dev/null
+++ b/scripts/Makefile.vmlinux_o
@@ -0,0 +1,98 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+PHONY := __default
+__default: vmlinux.o
+
+include include/config/auto.conf
+include $(srctree)/scripts/Kbuild.include
+
+# for objtool
+include $(srctree)/scripts/Makefile.lib
+
+# Generate a linker script to ensure correct ordering of initcalls for Clang LTO
+# ---------------------------------------------------------------------------
+
+quiet_cmd_gen_initcalls_lds = GEN     $@
+      cmd_gen_initcalls_lds = \
+	$(PYTHON3) $(srctree)/scripts/jobserver-exec \
+	$(PERL) $(real-prereqs) > $@
+
+.tmp_initcalls.lds: $(srctree)/scripts/generate_initcall_order.pl \
+		vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
+	$(call if_changed,gen_initcalls_lds)
+
+targets := .tmp_initcalls.lds
+
+ifdef CONFIG_LTO_CLANG
+initcalls-lds := .tmp_initcalls.lds
+endif
+
+# objtool for vmlinux.o
+# ---------------------------------------------------------------------------
+#
+# For delay-objtool (IBT or LTO), objtool doesn't run on individual translation
+# units.  Instead it runs on vmlinux.o.
+#
+# For !delay-objtool + CONFIG_NOINSTR_VALIDATION, it runs on both translation
+# units and vmlinux.o, with the latter only used for noinstr/unret validation.
+
+objtool-enabled := $(or $(delay-objtool),$(CONFIG_NOINSTR_VALIDATION))
+
+ifeq ($(delay-objtool),y)
+vmlinux-objtool-args-y					+= $(objtool-args-y)
+else
+vmlinux-objtool-args-$(CONFIG_OBJTOOL_WERROR)		+= --werror
+endif
+
+vmlinux-objtool-args-$(CONFIG_NOINSTR_VALIDATION)	+= --noinstr \
+							   $(if $(or $(CONFIG_MITIGATION_UNRET_ENTRY),$(CONFIG_MITIGATION_SRSO)), --unret)
+
+# Only used for builds initiated by klp-build
+vmlinux-objtool-args-$(if $(KLP_SYMIDS),y)		+= --klp-symids
+
+objtool-args = $(vmlinux-objtool-args-y) --link
+
+# Link of vmlinux.o used for section mismatch analysis
+# ---------------------------------------------------------------------------
+
+vmlinux-o-ld-args-$(CONFIG_BUILTIN_MODULE_RANGES)	+= -Map=$@.map
+
+quiet_cmd_ld_vmlinux.o = LD      $@
+      cmd_ld_vmlinux.o = \
+	$(LD) ${KBUILD_LDFLAGS} -r -o $@ \
+	$(vmlinux-o-ld-args-y) \
+	$(addprefix -T , $(initcalls-lds)) \
+	--whole-archive vmlinux.a --no-whole-archive \
+	--start-group $(KBUILD_VMLINUX_LIBS) --end-group \
+	$(cmd_objtool)
+
+cmd_check_function_names = $(srctree)/scripts/check-function-names.sh $@
+
+define rule_ld_vmlinux.o
+	$(call cmd_and_savecmd,ld_vmlinux.o)
+	$(call cmd,gen_objtooldep)
+	$(call cmd,check_function_names)
+endef
+
+
+vmlinux.o: $(initcalls-lds) vmlinux.a $(KBUILD_VMLINUX_LIBS) FORCE
+	$(call if_changed_rule,ld_vmlinux.o)
+
+targets += vmlinux.o
+
+# Add FORCE to the prerequisites of a target to force it to be always rebuilt.
+# ---------------------------------------------------------------------------
+
+PHONY += FORCE
+FORCE:
+
+# Read all saved command lines and dependencies for the $(targets) we
+# may be building above, using $(if_changed{,_dep}). As an
+# optimization, we don't need to read them if the target does not
+# exist, we will rebuild anyway in that case.
+
+existing-targets := $(wildcard $(sort $(targets)))
+
+-include $(foreach f,$(existing-targets),$(dir $(f)).$(notdir $(f)).cmd)
+
+.PHONY: $(PHONY)