thunderbolt: Fix NULL dereference in tb_remove_work()grafted

There is a slight race between tb_remove_work() and tb_domain_remove()
which leads to dereferencing a NULL tb->root_switch pointer inside
tb_free_unplugged_xdomains():

        Thread A                            Thread B

  tb_remove_work()
                                    tb_domain_remove()
                                      mutex_lock(&tb->lock)
                                      tb_stop()
                                        /* doesn't cancel a running callback */
                                        cancel_delayed_work(&tcm->remove_work)
                                        ...
                                        tb_switch_remove(tb->root_switch)
                                        tb->root_switch = NULL
                                      mutex_unlock(&tb->lock)
    mutex_lock(&tb->lock)
    ...
    /* without checking ->root_switch */
    tb_free_unplugged_xdomains(tb->root_switch)
    mutex_unlock(&tb->lock)

Commit a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without
holding tb->lock") doesn't seem right to move tb_free_unplugged_xdomains()
out of the &tb->lock section and the check for tb->root_switch, in
particular.  It states:

  For this reason separate removing the XDomain from the topology data
  structures (where we need the lock) from unregistering the device from
  the bus (where remove callbacks of the drivers are being called).

tb_free_unplugged_xdomains() belongs to the former group of functions
requiring the lock.  And it also calls tb_xdomain_remove() which should
only be called with &tb->lock held.

Found by Linux Verification Center (linuxtesting.org) with Svace static
analysis tool.

Fixes: a8937f35cf39 ("thunderbolt: Remove XDomain from the bus without holding tb->lock")
Cc: stable@vger.kernel.org
Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 103 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/Makefile b/Documentation/devicetree/bindings/Makefile
new file mode 100644
index 000000000..6b4b4f51c
--- /dev/null
+++ b/Documentation/devicetree/bindings/Makefile
@@ -0,0 +1,103 @@
+# SPDX-License-Identifier: GPL-2.0
+DT_DOC_CHECKER ?= dt-doc-validate
+DT_EXTRACT_EX ?= dt-extract-example
+DT_MK_SCHEMA ?= dt-mk-schema
+
+DT_SCHEMA_LINT = $(shell which yamllint || \
+  echo "warning: python package 'yamllint' not installed, skipping" >&2)
+
+DT_SCHEMA_MIN_VERSION = 2024.4
+
+PHONY += check_dtschema_version
+check_dtschema_version:
+	@which $(DT_DOC_CHECKER) >/dev/null || \
+		{ echo "Error: '$(DT_DOC_CHECKER)' not found!" >&2; \
+		  echo "Ensure dtschema python package is installed and in your PATH." >&2; \
+		  echo "Current PATH is:" >&2; \
+		  echo "$$PATH" >&2; false; }
+	@{ echo $(DT_SCHEMA_MIN_VERSION); \
+	$(DT_DOC_CHECKER) --version 2>/dev/null || echo 0; } | sort -Vc >/dev/null || \
+	{ echo "ERROR: dtschema minimum version is v$(DT_SCHEMA_MIN_VERSION)" >&2; false; }
+
+quiet_cmd_extract_ex = DTEX    $@
+      cmd_extract_ex = $(DT_EXTRACT_EX) $< > $@
+
+$(obj)/%.example.dts: $(src)/%.yaml check_dtschema_version FORCE
+	$(call if_changed,extract_ex)
+
+find_all_cmd = find $(src) \( -name '*.yaml' ! \
+		-name 'processed-schema*' \)
+
+find_cmd = $(find_all_cmd) | \
+		sed 's|^$(srctree)/||' | \
+		grep -F -e "$(subst :," -e ",$(DT_SCHEMA_FILES))" | \
+		sed 's|^|$(srctree)/|'
+CHK_DT_EXAMPLES := $(patsubst $(srctree)/%.yaml,%.example.dtb, \
+			      $(shell $(find_cmd) | xargs grep -l '^examples:'))
+
+quiet_cmd_yamllint = LINT    $(src)
+      cmd_yamllint = ($(find_cmd) | \
+                     xargs -n200 -P$$(nproc) \
+		     $(DT_SCHEMA_LINT) -f parsable -c $(src)/.yamllint >&2) \
+		     && touch $@ || true
+
+quiet_cmd_chk_bindings = CHKDT   $(src)
+      cmd_chk_bindings = ($(find_cmd) | \
+			  xargs -n200 -P$$(nproc) $(DT_DOC_CHECKER) -u $(src)) \
+			  && touch $@ || true
+
+DT_CHK_STYLE = $(srctree)/scripts/dtc/dt-check-style
+
+# Feed the file list to the checker via @argfile in a single Python
+# process so the ruamel.yaml import is paid once. scripts/jobserver-exec
+# claims slots from the GNU make jobserver and exposes the count via
+# $PARALLELISM, which dt-check-style picks up to size its worker pool.
+quiet_cmd_chk_style = STYLE   $(src)
+      cmd_chk_style = f=$$(mktemp) && $(find_cmd) > $$f && \
+		      $(PYTHON3) $(srctree)/scripts/jobserver-exec \
+		      $(PYTHON3) $(DT_CHK_STYLE) @$$f \
+		      && touch $@ || true; rm -f $$f
+
+quiet_cmd_mk_schema = SCHEMA  $@
+      cmd_mk_schema = f=$$(mktemp) ; \
+                      $(find_all_cmd) > $$f ; \
+                      $(DT_MK_SCHEMA) -j $(DT_MK_SCHEMA_FLAGS) @$$f > $@ ; \
+		      rm -f $$f
+
+DT_DOCS = $(patsubst $(srctree)/%,%,$(shell $(find_all_cmd)))
+
+override DTC_FLAGS := \
+	-Wno-avoid_unnecessary_addr_size \
+	-Wno-unique_unit_address \
+	-Wunique_unit_address_if_enabled
+
+$(obj)/processed-schema.json: $(DT_DOCS) check_dtschema_version FORCE
+	$(call if_changed,mk_schema)
+
+targets += .dt-binding.checked .yamllint.checked .dt-style.checked
+$(obj)/.yamllint.checked: $(DT_DOCS) $(src)/.yamllint FORCE
+	$(if $(DT_SCHEMA_LINT),$(call if_changed,yamllint),)
+
+$(obj)/.dt-binding.checked: $(DT_DOCS) FORCE
+	$(call if_changed,chk_bindings)
+
+$(obj)/.dt-style.checked: $(DT_DOCS) FORCE
+	$(call if_changed,chk_style)
+
+always-y += processed-schema.json
+targets += $(patsubst $(obj)/%,%, $(CHK_DT_EXAMPLES))
+targets += $(patsubst $(obj)/%.dtb,%.dts, $(CHK_DT_EXAMPLES))
+
+# Hack: avoid 'Argument list too long' error for 'make clean'. Remove most of
+# build artifacts here before they are processed by scripts/Makefile.clean
+clean-files = $(shell find $(obj) \( -name '*.example.dts' -o \
+			-name '*.example.dtb' \) -delete 2>/dev/null)
+
+dt_compatible_check: $(obj)/processed-schema.json
+	$(Q)$(srctree)/scripts/dtc/dt-extract-compatibles $(srctree) | xargs dt-check-compatible -v -s $<
+
+PHONY += dt_binding_check_one
+dt_binding_check_one: $(obj)/.dt-binding.checked $(obj)/.yamllint.checked $(obj)/.dt-style.checked
+
+PHONY += dt_binding_check
+dt_binding_check: dt_binding_check_one $(CHK_DT_EXAMPLES)