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, 273 insertions, 0 deletions

diff --git a/scripts/package/mkdebian b/scripts/package/mkdebian
new file mode 100755
index 000000000..d4b007b38
--- /dev/null
+++ b/scripts/package/mkdebian
@@ -0,0 +1,273 @@
+#!/bin/sh
+#
+# Copyright 2003 Wichert Akkerman <wichert@wiggy.net>
+#
+# Simple script to generate a debian/ directory for a Linux kernel.
+
+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 "$3"
+	fi
+}
+
+set_debarch() {
+	if [ "${KBUILD_DEBARCH:+set}" ]; then
+		debarch="$KBUILD_DEBARCH"
+		return
+	fi
+
+	# Attempt to find the correct Debian architecture
+	case "$UTS_MACHINE" in
+	i386|alpha|m68k|riscv*)
+		debarch="$UTS_MACHINE" ;;
+	x86_64)
+		debarch=amd64 ;;
+	sparc*)
+		debarch=sparc$(if_enabled_echo CONFIG_64BIT 64) ;;
+	s390*)
+		debarch=s390x ;;
+	ppc*)
+		if is_enabled CONFIG_64BIT; then
+			debarch=ppc64$(if_enabled_echo CONFIG_CPU_LITTLE_ENDIAN el)
+		else
+			debarch=powerpc$(if_enabled_echo CONFIG_SPE spe)
+		fi
+		;;
+	parisc*)
+		debarch=hppa ;;
+	mips*)
+		if is_enabled CONFIG_CPU_LITTLE_ENDIAN; then
+			debarch=mips$(if_enabled_echo CONFIG_64BIT 64)$(if_enabled_echo CONFIG_CPU_MIPSR6 r6)el
+		elif is_enabled CONFIG_CPU_MIPSR6; then
+			debarch=mips$(if_enabled_echo CONFIG_64BIT 64)r6
+		else
+			debarch=mips
+		fi
+		;;
+	aarch64|arm64)
+		debarch=arm64 ;;
+	arm*)
+		if is_enabled CONFIG_AEABI; then
+			debarch=arm$(if_enabled_echo CONFIG_VFP hf el)
+		else
+			debarch=arm
+		fi
+		;;
+	openrisc)
+		debarch=or1k ;;
+	sh)
+		if is_enabled CONFIG_CPU_SH3; then
+			debarch=sh3$(if_enabled_echo CONFIG_CPU_BIG_ENDIAN eb)
+		elif is_enabled CONFIG_CPU_SH4; then
+			debarch=sh4$(if_enabled_echo CONFIG_CPU_BIG_ENDIAN eb)
+		fi
+		;;
+	um)
+		if is_enabled CONFIG_64BIT; then
+			debarch=amd64
+		else
+			debarch=i386
+		fi
+		;;
+	loongarch64)
+		debarch=loong64 ;;
+	esac
+	if [ -z "$debarch" ]; then
+		debarch=$(dpkg-architecture -qDEB_HOST_ARCH)
+		echo "" >&2
+		echo "** ** **  WARNING  ** ** **" >&2
+		echo "" >&2
+		echo "Your architecture doesn't have its equivalent" >&2
+		echo "Debian userspace architecture defined!" >&2
+		echo "Falling back to the current host architecture ($debarch)." >&2
+		echo "Please add support for $UTS_MACHINE to ${0} ..." >&2
+		echo "" >&2
+	fi
+}
+
+# Create debian/source/ if it is a source package build
+gen_source ()
+{
+	mkdir -p debian/source
+
+	echo "3.0 (quilt)" > debian/source/format
+
+	{
+		echo "diff-ignore"
+		echo "extend-diff-ignore = .*"
+	} > debian/source/local-options
+
+	# Add .config as a patch
+	mkdir -p debian/patches
+	{
+		echo "Subject: Add .config"
+		echo "Author: ${maintainer}"
+		echo
+		echo "--- /dev/null"
+		echo "+++ linux/.config"
+		diff -u /dev/null "${KCONFIG_CONFIG}" | tail -n +3
+	} > debian/patches/config.patch
+	echo config.patch > debian/patches/series
+
+	"${srctree}/scripts/package/gen-diff-patch" debian/patches/diff.patch
+	if [ -s debian/patches/diff.patch ]; then
+		sed -i "
+			1iSubject: Add local diff
+			1iAuthor: ${maintainer}
+			1i
+		" debian/patches/diff.patch
+
+		echo diff.patch >> debian/patches/series
+	else
+		rm -f debian/patches/diff.patch
+	fi
+}
+
+rm -rf debian
+mkdir debian
+
+user=${KBUILD_BUILD_USER:-$(id -nu)}
+name=${DEBFULLNAME:-${user}}
+if [ "${DEBEMAIL:+set}" ]; then
+	email=${DEBEMAIL}
+else
+	buildhost=${KBUILD_BUILD_HOST:-$(hostname -f 2>/dev/null || hostname)}
+	email="${user}@${buildhost}"
+fi
+maintainer="${name} <${email}>"
+
+while [ $# -gt 0 ]; do
+	case "$1" in
+	--need-source)
+		gen_source
+		shift
+		;;
+	*)
+		break
+		;;
+	esac
+done
+
+# Some variables and settings used throughout the script
+if [ "${KDEB_PKGVERSION:+set}" ]; then
+	packageversion=$KDEB_PKGVERSION
+else
+	upstream_version=$("${srctree}/scripts/setlocalversion" --no-local "${srctree}" | sed 's/-\(rc[1-9]\)/~\1/')
+	debian_revision=$("${srctree}/scripts/build-version")
+	packageversion=${upstream_version}-${debian_revision}
+fi
+sourcename=${KDEB_SOURCENAME:-linux-upstream}
+
+if [ "$ARCH" = "um" ] ; then
+	packagename=user-mode-linux
+else
+	packagename=linux-image
+fi
+
+debarch=
+set_debarch
+
+# Try to determine distribution
+if [ "${KDEB_CHANGELOG_DIST:+set}" ]; then
+        distribution=$KDEB_CHANGELOG_DIST
+# In some cases lsb_release returns the codename as n/a, which breaks dpkg-parsechangelog
+elif distribution=$(lsb_release -cs 2>/dev/null) && [ -n "$distribution" ] && [ "$distribution" != "n/a" ]; then
+        : # nothing to do in this case
+else
+        distribution="unstable"
+        echo >&2 "Using default distribution of 'unstable' in the changelog"
+        echo >&2 "Install lsb-release or set \$KDEB_CHANGELOG_DIST explicitly"
+fi
+
+echo $debarch > debian/arch
+
+host_gnu=$(dpkg-architecture -a "${debarch}" -q DEB_HOST_GNU_TYPE | sed 's/_/-/g')
+
+# Generate a simple changelog template
+cat <<EOF > debian/changelog
+$sourcename ($packageversion) $distribution; urgency=low
+
+  * Custom built Linux kernel.
+
+ -- $maintainer  $(date -R)
+EOF
+
+# Generate a control file
+cat <<EOF > debian/control
+Source: $sourcename
+Section: kernel
+Priority: optional
+Maintainer: $maintainer
+Rules-Requires-Root: no
+Build-Depends: debhelper-compat (= 12)
+Build-Depends-Arch: bc, bison, flex,
+ gcc-${host_gnu} <!pkg.${sourcename}.nokernelheaders>,
+ kmod, libdw-dev:native, libelf-dev:native,
+ libssl-dev:native, libssl-dev <!pkg.${sourcename}.nokernelheaders>,
+ python3:native, rsync
+Homepage: https://www.kernel.org/
+
+Package: $packagename-${KERNELRELEASE}
+Architecture: $debarch
+Description: Linux kernel, version ${KERNELRELEASE}
+ This package contains the Linux kernel, modules and corresponding other
+ files, version: ${KERNELRELEASE}.
+EOF
+
+if [ "${SRCARCH}" != um ]; then
+cat <<EOF >> debian/control
+
+Package: linux-libc-dev
+Section: devel
+Provides: linux-kernel-headers
+Architecture: $debarch
+Description: Linux support headers for userspace development
+ This package provides userspaces headers from the Linux kernel.  These headers
+ are used by the installed headers for GNU glibc and other system libraries.
+Multi-Arch: same
+EOF
+
+if is_enabled CONFIG_MODULES; then
+cat <<EOF >> debian/control
+
+Package: linux-headers-${KERNELRELEASE}
+Architecture: $debarch
+Build-Profiles: <!pkg.${sourcename}.nokernelheaders>
+Description: Linux kernel headers for ${KERNELRELEASE} on $debarch
+ This package provides kernel header files for ${KERNELRELEASE} on $debarch
+ .
+ This is useful for people who need to build external modules
+EOF
+fi
+fi
+
+if is_enabled CONFIG_DEBUG_INFO; then
+cat <<EOF >> debian/control
+
+Package: linux-image-${KERNELRELEASE}-dbg
+Section: debug
+Architecture: $debarch
+Build-Profiles: <!pkg.${sourcename}.nokerneldbg>
+Description: Linux kernel debugging symbols for ${KERNELRELEASE}
+ This package will come in handy if you need to debug the kernel. It provides
+ all the necessary debug symbols for the kernel and its modules.
+EOF
+fi
+
+cat <<EOF > debian/rules.vars
+ARCH := ${ARCH}
+KERNELRELEASE := ${KERNELRELEASE}
+EOF
+
+cp "${srctree}/scripts/package/debian/copyright" debian/
+cp "${srctree}/scripts/package/debian/rules" debian/
+
+exit 0