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>

2 files changed, 113 insertions, 0 deletions

diff --git a/scripts/package/debian/copyright b/scripts/package/debian/copyright
new file mode 100644
index 000000000..4f1f06221
--- /dev/null
+++ b/scripts/package/debian/copyright
@@ -0,0 +1,16 @@
+This is a packaged upstream version of the Linux kernel.
+
+The sources may be found at most Linux archive sites, including:
+https://www.kernel.org/pub/linux/kernel
+
+Copyright: 1991 - 2023 Linus Torvalds and others.
+
+The git repository for mainline kernel development is at:
+git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; version 2 dated June, 1991.
+
+On Debian GNU/Linux systems, the complete text of the GNU General Public
+License version 2 can be found in `/usr/share/common-licenses/GPL-2'.
diff --git a/scripts/package/debian/rules b/scripts/package/debian/rules
new file mode 100755
index 000000000..a417a7f8b
--- /dev/null
+++ b/scripts/package/debian/rules
@@ -0,0 +1,97 @@
+#!/usr/bin/make -f
+# SPDX-License-Identifier: GPL-2.0-only
+
+# in case debian/rules is executed directly
+export DEB_RULES_REQUIRES_ROOT := no
+
+include debian/rules.vars
+
+ifneq (,$(filter-out parallel=1,$(filter parallel=%,$(DEB_BUILD_OPTIONS))))
+    NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
+    MAKEFLAGS += -j$(NUMJOBS)
+endif
+
+# When KBUILD_VERBOSE is undefined (presumably you are directly working with
+# the debianized tree), show verbose logs unless DEB_BUILD_OPTION=terse is set.
+ifeq ($(origin KBUILD_VERBOSE),undefined)
+    ifeq (,$(filter terse,$(DEB_BUILD_OPTIONS)))
+        export KBUILD_VERBOSE := 1
+    else
+        Q := @
+    endif
+endif
+
+revision = $(shell dpkg-parsechangelog -S Version | sed -n 's/.*-//p')
+CROSS_COMPILE ?= $(filter-out $(DEB_BUILD_GNU_TYPE)-, $(DEB_HOST_GNU_TYPE)-)
+make-opts = ARCH=$(ARCH) KERNELRELEASE=$(KERNELRELEASE) \
+    $(addprefix KBUILD_BUILD_VERSION=,$(revision)) \
+    $(addprefix CROSS_COMPILE=,$(CROSS_COMPILE))
+
+binary-targets := $(addprefix binary-, image image-dbg headers libc-dev)
+
+all-packages = $(shell dh_listpackages)
+image-package = $(filter linux-image-% user-%, $(filter-out %-dbg, $(all-packages)))
+image-dbg-package = $(filter %-dbg, $(all-packages))
+libc-dev-package = $(filter linux-libc-dev, $(all-packages))
+headers-package = $(filter linux-headers-%, $(all-packages))
+
+mk-files = $(patsubst binary-%,debian/%.files,$1)
+package = $($(@:binary-%=%-package))
+
+# DH_OPTION is an environment variable common for all debhelper commands.
+# We could 'export' it, but here it is passed from the command line to clarify
+# which package is being processed in the build log.
+DH_OPTIONS = -p$(package)
+
+# Note: future removal of KDEB_COMPRESS
+# dpkg-deb >= 1.21.10 supports the DPKG_DEB_COMPRESSOR_TYPE environment
+# variable, which provides the same functionality as KDEB_COMPRESS. The
+# KDEB_COMPRESS variable will be removed in the future.
+define binary
+	$(Q)dh_testdir $(DH_OPTIONS)
+	$(Q)dh_testroot $(DH_OPTIONS)
+	$(Q)dh_prep $(DH_OPTIONS)
+	$(Q)+$(MAKE) $(make-opts) run-command KBUILD_RUN_COMMAND='+$$(srctree)/scripts/package/builddeb $(package)'
+	$(Q)dh_installdocs $(DH_OPTIONS)
+	$(Q)dh_installchangelogs $(DH_OPTIONS)
+	$(Q)dh_compress $(DH_OPTIONS)
+	$(Q)dh_fixperms $(DH_OPTIONS)
+	$(Q)dh_gencontrol $(DH_OPTIONS) -- -f$(call mk-files,$@)
+	$(Q)dh_md5sums $(DH_OPTIONS)
+	$(Q)dh_builddeb $(DH_OPTIONS) -- $(addprefix -Z,$(KDEB_COMPRESS))
+endef
+
+.PHONY: $(binary-targets)
+$(binary-targets): build-arch
+	$(Q)truncate -s0 $(call mk-files,$@)
+	$(if $(package),$(binary))
+
+.PHONY: binary binary-indep binary-arch
+binary: binary-arch binary-indep
+binary-indep: build-indep
+binary-arch: $(binary-targets)
+	$(Q)cat $(call mk-files,$^) > debian/files
+
+.PHONY: build build-indep build-arch
+build: build-arch build-indep
+build-indep:
+build-arch:
+	$(Q)$(MAKE) $(make-opts) olddefconfig
+	$(Q)$(MAKE) $(make-opts) $(if $(filter um,$(ARCH)),,headers) all
+
+.PHONY: clean
+clean:
+	$(Q)dh_clean
+	$(Q)rm -rf debian/deb-env.vars* debian/*.files
+	$(Q)$(MAKE) ARCH=$(ARCH) clean
+
+# If DEB_HOST_ARCH is empty, it is likely that debian/rules was executed
+# directly. Run 'dpkg-architecture --print-set --print-format=make' to
+# generate a makefile construct that exports all DEB_* variables.
+ifndef DEB_HOST_ARCH
+include debian/deb-env.vars
+
+debian/deb-env.vars:
+	$(Q)dpkg-architecture -a$$(cat debian/arch) --print-set --print-format=make > $@.tmp
+	$(Q)mv $@.tmp $@
+endif