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, 176 insertions, 0 deletions

diff --git a/scripts/package/builddeb b/scripts/package/builddeb
new file mode 100755
index 000000000..ba1defc61
--- /dev/null
+++ b/scripts/package/builddeb
@@ -0,0 +1,176 @@
+#!/bin/sh
+#
+# builddeb 1.3
+# Copyright 2003 Wichert Akkerman <wichert@wiggy.net>
+#
+# Simple script to generate a deb package for a Linux kernel. All the
+# complexity of what to do with a kernel after it is installed or removed
+# is left to other scripts and packages. Scripts can be placed into the
+# preinst, postinst, prerm and postrm directories in /etc/kernel or
+# /usr/share/kernel. A different list of search directories can be given
+# via KDEB_HOOKDIR. Scripts in directories earlier in the list will
+# override scripts of the same name in later directories.  The script will
+# be called on package installation and removal.
+
+set -eu
+
+is_enabled() {
+	grep -q "^$1=y" include/config/auto.conf
+}
+
+if_enabled_echo() {
+	if is_enabled "$1"; then
+		echo -n "$2"
+	elif [ $# -ge 3 ]; then
+		echo -n "$3"
+	fi
+}
+
+install_linux_image () {
+	pname=$1
+	pdir=debian/$1
+
+	# Only some architectures with OF support have this target
+	if is_enabled CONFIG_OF_EARLY_FLATTREE && [ -d "${srctree}/arch/${SRCARCH}/boot/dts" ]; then
+		${MAKE} -f ${srctree}/Makefile INSTALL_DTBS_PATH="${pdir}/usr/lib/linux-image-${KERNELRELEASE}" dtbs_install
+	fi
+
+	${MAKE} -f ${srctree}/Makefile INSTALL_MOD_PATH="${pdir}" INSTALL_MOD_STRIP=1 modules_install
+	rm -f "${pdir}/lib/modules/${KERNELRELEASE}/build"
+
+	# Install the kernel
+	if [ "${ARCH}" = um ] ; then
+		mkdir -p "${pdir}/usr/lib/uml/modules"
+		mv "${pdir}/lib/modules/${KERNELRELEASE}" "${pdir}/usr/lib/uml/modules/${KERNELRELEASE}"
+		mkdir -p "${pdir}/usr/bin" "${pdir}/usr/share/doc/${pname}"
+		cp System.map "${pdir}/usr/lib/uml/modules/${KERNELRELEASE}/System.map"
+		cp ${KCONFIG_CONFIG} "${pdir}/usr/share/doc/${pname}/config"
+		gzip "${pdir}/usr/share/doc/${pname}/config"
+	else
+		mkdir -p "${pdir}/boot"
+		cp System.map "${pdir}/boot/System.map-${KERNELRELEASE}"
+		cp ${KCONFIG_CONFIG} "${pdir}/boot/config-${KERNELRELEASE}"
+	fi
+
+	# Not all arches have the same installed path in debian
+	# XXX: have each arch Makefile export a variable of the canonical image install
+	# path instead
+	case "${SRCARCH}" in
+	um)
+		installed_image_path="usr/bin/linux-${KERNELRELEASE}";;
+	parisc|mips|powerpc)
+		installed_image_path="boot/vmlinux-${KERNELRELEASE}";;
+	*)
+		installed_image_path="boot/vmlinuz-${KERNELRELEASE}";;
+	esac
+	cp "$(${MAKE} -s -f ${srctree}/Makefile image_name)" "${pdir}/${installed_image_path}"
+
+	if [ "${ARCH}" != um ]; then
+		install_maint_scripts "${pdir}"
+	fi
+}
+
+install_maint_scripts () {
+	# Install the maintainer scripts
+	# Note: hook scripts under /etc/kernel are also executed by official Debian
+	# kernel packages, as well as kernel packages built using make-kpkg.
+	# make-kpkg sets $INITRD to indicate whether an initramfs is wanted, and
+	# so do we; recent versions of dracut and initramfs-tools will obey this.
+	debhookdir=${KDEB_HOOKDIR:-/etc/kernel /usr/share/kernel}
+	for script in postinst postrm preinst prerm; do
+		mkdir -p "${pdir}/DEBIAN"
+		cat <<-EOF > "${pdir}/DEBIAN/${script}"
+		#!/bin/sh
+
+		set -e
+
+		# Pass maintainer script parameters to hook scripts
+		export DEB_MAINT_PARAMS="\$*"
+
+		# Tell initramfs builder whether it's wanted
+		export INITRD=$(if_enabled_echo CONFIG_BLK_DEV_INITRD Yes No)
+
+		# run-parts will error out if one of its directory arguments does not
+		# exist, so filter the list of hook directories accordingly.
+		hookdirs=
+		for dir in ${debhookdir}; do
+			test -d "\$dir/${script}.d" || continue
+			hookdirs="\$hookdirs \$dir/${script}.d"
+		done
+		hookdirs="\${hookdirs# }"
+		test -n "\$hookdirs" && run-parts --arg="${KERNELRELEASE}" --arg="/${installed_image_path}" \$hookdirs
+		exit 0
+		EOF
+		chmod 755 "${pdir}/DEBIAN/${script}"
+	done
+}
+
+install_linux_image_dbg () {
+	pdir=debian/$1
+
+	# Parse modules.order directly because 'make modules_install' may sign,
+	# compress modules, and then run unneeded depmod.
+	if is_enabled CONFIG_MODULES; then
+		while read -r mod; do
+			mod="${mod%.o}.ko"
+			dbg="${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/kernel/${mod}"
+			buildid=$("${READELF}" -n "${mod}" | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+			link="${pdir}/usr/lib/debug/.build-id/${buildid}.debug"
+
+			mkdir -p "${dbg%/*}" "${link%/*}"
+			"${OBJCOPY}" --only-keep-debug "${mod}" "${dbg}"
+			ln -sf --relative "${dbg}" "${link}"
+		done < modules.order
+	fi
+
+	# Build debug package
+	# Different tools want the image in different locations
+	# perf
+	mkdir -p ${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/
+	cp vmlinux ${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/
+	# systemtap
+	mkdir -p ${pdir}/usr/lib/debug/boot/
+	ln -s ../lib/modules/${KERNELRELEASE}/vmlinux ${pdir}/usr/lib/debug/boot/vmlinux-${KERNELRELEASE}
+	# kdump-tools
+	ln -s lib/modules/${KERNELRELEASE}/vmlinux ${pdir}/usr/lib/debug/vmlinux-${KERNELRELEASE}
+}
+
+install_kernel_headers () {
+	pdir=debian/$1
+	version=${1#linux-headers-}
+
+	# Override $CC only for cross-compiles, to not unnecessarily rebuild
+	# scripts/ including plugins, which may lead to a full kernel rebuild.
+	if [ -n "${CROSS_COMPILE}" ]; then
+		CC="${DEB_HOST_GNU_TYPE}-gcc" "${srctree}/scripts/package/install-extmod-build" "${pdir}/usr/src/linux-headers-${version}"
+	else
+		"${srctree}/scripts/package/install-extmod-build" "${pdir}/usr/src/linux-headers-${version}"
+	fi
+
+	mkdir -p $pdir/lib/modules/$version/
+	ln -s /usr/src/linux-headers-$version $pdir/lib/modules/$version/build
+}
+
+install_libc_headers () {
+	pdir=debian/$1
+
+	$MAKE -f $srctree/Makefile headers_install INSTALL_HDR_PATH=$pdir/usr
+
+	# move asm headers to /usr/include/<libc-machine>/asm to match the structure
+	# used by Debian-based distros (to support multi-arch)
+	mkdir "$pdir/usr/include/${DEB_HOST_MULTIARCH}"
+	mv "$pdir/usr/include/asm" "$pdir/usr/include/${DEB_HOST_MULTIARCH}"
+}
+
+package=$1
+
+case "${package}" in
+*-dbg)
+	install_linux_image_dbg "${package}";;
+linux-image-*|user-mode-linux-*)
+	install_linux_image "${package}";;
+linux-libc-dev)
+	install_libc_headers "${package}";;
+linux-headers-*)
+	install_kernel_headers "${package}";;
+esac