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, 361 insertions, 0 deletions

diff --git a/scripts/dtc/dtx_diff b/scripts/dtc/dtx_diff
new file mode 100755
index 000000000..f2bbde4bb
--- /dev/null
+++ b/scripts/dtc/dtx_diff
@@ -0,0 +1,361 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0-only
+
+# Copyright (C) 2015 Frank Rowand
+#
+
+
+usage() {
+
+	# use spaces instead of tabs in the usage message
+	cat >&2 <<eod
+
+Usage:
+
+   `basename $0` DTx
+        decompile DTx
+
+   `basename $0` DTx_1 DTx_2
+        diff DTx_1 and DTx_2
+
+
+      --annotate    synonym for -T
+      --color       synonym for -c (requires diff with --color support)
+       -c           enable colored output
+       -f           print full dts in diff (--unified=99999)
+       -h           synonym for --help
+       -help        synonym for --help
+      --help        print this message and exit
+       -s SRCTREE   linux kernel source tree is at path SRCTREE
+                        (default is current directory)
+       -S           linux kernel source tree is at root of current git repo
+       -T           annotate output .dts with input source file and line
+                        (-T -T for more details)
+       -u           unsorted, do not sort DTx
+
+
+Each DTx is processed by the dtc compiler to produce a sorted dts source
+file.  If DTx is a dts source file then it is pre-processed in the same
+manner as done for the compile of the dts source file in the Linux kernel
+build system ('#include' and '/include/' directives are processed).
+
+If two DTx are provided, the resulting dts source files are diffed.
+
+If DTx is a directory, it is treated as a DT subtree, such as
+  /proc/device-tree.
+
+If DTx contains the binary blob magic value in the first four bytes,
+  it is treated as a binary blob (aka .dtb or FDT).
+
+Otherwise DTx is treated as a dts source file (aka .dts).
+
+   If this script is not run from the root of the linux source tree,
+   and DTx utilizes '#include' or '/include/' then the path of the
+   linux source tree can be provided by '-s SRCTREE' or '-S' so that
+   include paths will be set properly.
+
+   The shell variable \${ARCH} must provide the architecture containing
+   the dts source file for include paths to be set properly for '#include'
+   or '/include/' to be processed.
+
+   If DTx_1 and DTx_2 are in different architectures, then this script
+   may not work since \${ARCH} is part of the include path.  The following
+   workaround can be used:
+
+      `basename $0` ARCH=arch_of_dtx_1 DTx_1 >tmp_dtx_1.dts
+      `basename $0` ARCH=arch_of_dtx_2 DTx_2 >tmp_dtx_2.dts
+      `basename $0` tmp_dtx_1.dts tmp_dtx_2.dts
+      rm tmp_dtx_1.dts tmp_dtx_2.dts
+
+   If DTx_1 and DTx_2 are in different directories, then this script will
+   add the path of DTx_1 and DTx_2 to the include paths.  If DTx_2 includes
+   a local file that exists in both the path of DTx_1 and DTx_2 then the
+   file in the path of DTx_1 will incorrectly be included.  Possible
+   workaround:
+
+      `basename $0` DTx_1 >tmp_dtx_1.dts
+      `basename $0` DTx_2 >tmp_dtx_2.dts
+      `basename $0` tmp_dtx_1.dts tmp_dtx_2.dts
+      rm tmp_dtx_1.dts tmp_dtx_2.dts
+
+eod
+}
+
+
+compile_to_dts() {
+
+	dtx="$1"
+	dtc_include="$2"
+
+	if [ -d "${dtx}" ] ; then
+
+		# -----  input is file tree
+
+		if ( ! ${DTC} -I fs ${dtx} ) ; then
+			exit 3
+		fi
+
+	elif [ -f "${dtx}" ] && [ -r "${dtx}" ] ; then
+
+		magic=`hexdump -n 4 -e '/1 "%02x"' ${dtx}`
+		if [ "${magic}" = "d00dfeed" ] ; then
+
+			# -----  input is FDT (binary blob)
+
+			if ( ! ${DTC} -I dtb ${dtx} ) ; then
+				exit 3
+			fi
+
+			return
+
+		fi
+
+		# -----  input is DTS (source)
+
+		if ( cpp ${cpp_flags} -x assembler-with-cpp ${dtx} \
+			| ${DTC} ${dtc_include} -I dts ) ; then
+			return
+		fi
+
+		echo ""                                                      >&2
+		echo "Possible hints to resolve the above error:"            >&2
+		echo "  (hints might not fix the problem)"                   >&2
+
+		hint_given=0
+
+		if [ "${ARCH}" = "" ] ; then
+			hint_given=1
+			echo ""                                              >&2
+			echo "  shell variable \$ARCH not set"               >&2
+		fi
+
+		dtx_arch=`echo "/${dtx}" | sed -e 's|.*/arch/||' -e 's|/.*||'`
+
+		if [ "${dtx_arch}" != ""  -a "${dtx_arch}" != "${ARCH}" ] ; then
+			hint_given=1
+			echo ""                                              >&2
+			echo "  architecture ${dtx_arch} is in file path,"   >&2
+			echo "  but does not match shell variable \$ARCH"    >&2
+			echo "  >>\$ARCH<< is: >>${ARCH}<<"                  >&2
+		fi
+
+		if [ ! -d ${srctree}/arch/${ARCH} ] ; then
+			hint_given=1
+			echo ""                                              >&2
+			echo "  ${srctree}/arch/${ARCH}/ does not exist"     >&2
+			echo "  Is \$ARCH='${ARCH}' correct?"                >&2
+			echo "  Possible fix: use '-s' option"               >&2
+
+			git_root=`git rev-parse --show-toplevel 2>/dev/null`
+			if [ -d ${git_root}/arch/ ] ; then
+				echo "  Possible fix: use '-S' option"       >&2
+			fi
+		fi
+
+		if [ $hint_given = 0 ] ; then
+			echo ""                                              >&2
+			echo "  No hints available."                         >&2
+		fi
+
+		echo ""                                                      >&2
+
+		exit 3
+
+	else
+		echo ""                                                     >&2
+		echo "ERROR: ${dtx} does not exist or is not readable"      >&2
+		echo ""                                                     >&2
+		exit 2
+	fi
+
+}
+
+
+# -----  start of script
+
+annotate=""
+cmd_diff=0
+diff_flags="-u"
+diff_color=""
+dtx_file_1=""
+dtx_file_2=""
+dtc_sort="-s"
+help=0
+srctree=""
+
+
+while [ $# -gt 0 ] ; do
+
+	case $1 in
+
+	-c | --color )
+		if diff --color /dev/null /dev/null 2>/dev/null ; then
+			diff_color="--color=always"
+		fi
+		shift
+		;;
+
+	-f )
+		diff_flags="--unified=999999"
+		shift
+		;;
+
+	-h | -help | --help )
+		help=1
+		shift
+		;;
+
+	-s )
+		srctree="$2"
+		shift 2
+		;;
+
+	-S )
+		git_root=`git rev-parse --show-toplevel 2>/dev/null`
+		srctree="${git_root}"
+		shift
+		;;
+
+	-T | --annotate )
+		if [ "${annotate}"  = "" ] ; then
+			annotate="-T"
+		elif [ "${annotate}"  = "-T" ] ; then
+			annotate="-T -T"
+		fi
+		shift
+		;;
+	-u )
+		dtc_sort=""
+		shift
+		;;
+
+	*)
+		if [ "${dtx_file_1}"  = "" ] ; then
+			dtx_file_1="$1"
+		elif [ "${dtx_file_2}" = "" ] ; then
+			dtx_file_2="$1"
+		else
+			echo ""                                             >&2
+			echo "ERROR: Unexpected parameter: $1"              >&2
+			echo ""                                             >&2
+			exit 2
+		fi
+		shift
+		;;
+
+	esac
+
+done
+
+if [ "${srctree}" = "" ] ; then
+	srctree="."
+fi
+
+if [ "${dtx_file_2}" != "" ]; then
+	cmd_diff=1
+fi
+
+if (( ${help} )) ; then
+	usage
+	exit 1
+fi
+
+# this must follow check for ${help}
+if [ "${dtx_file_1}" = "" ]; then
+	echo ""                                                             >&2
+	echo "ERROR: parameter DTx required"                                >&2
+	echo ""                                                             >&2
+	exit 2
+fi
+
+
+# -----  prefer dtc from linux kernel, allow fallback to dtc in $PATH
+
+if [ "${KBUILD_OUTPUT:0:2}" = ".." ] ; then
+	__KBUILD_OUTPUT="${srctree}/${KBUILD_OUTPUT}"
+elif [ "${KBUILD_OUTPUT}" = "" ] ; then
+	__KBUILD_OUTPUT="."
+else
+	__KBUILD_OUTPUT="${KBUILD_OUTPUT}"
+fi
+
+DTC="${__KBUILD_OUTPUT}/scripts/dtc/dtc"
+
+if [ ! -x ${DTC} ] ; then
+	__DTC="dtc"
+	if grep -q "^CONFIG_DTC=y" ${__KBUILD_OUTPUT}/.config 2>/dev/null; then
+		make_command='
+         make scripts'
+	else
+		make_command='
+         Enable CONFIG_DTC in the kernel configuration
+         make scripts'
+	fi
+	if ( ! which ${__DTC} >/dev/null ) ; then
+
+		# use spaces instead of tabs in the error message
+		cat >&2 <<eod
+
+ERROR: unable to find a 'dtc' program
+
+   Preferred 'dtc' (built from Linux kernel source tree) was not found or
+   is not executable.
+
+      'dtc' is: ${DTC}
+
+      If it does not exist, create it from the root of the Linux source tree:
+${make_command}
+
+      If not at the root of the Linux kernel source tree -s SRCTREE or -S
+      may need to be specified to find 'dtc'.
+
+      If 'O=\${dir}' is specified in your Linux builds, this script requires
+      'export KBUILD_OUTPUT=\${dir}' or add \${dir}/scripts/dtc to \$PATH
+      before running.
+
+      If \${KBUILD_OUTPUT} is a relative path, then '-s SRCDIR', -S, or run
+      this script from the root of the Linux kernel source tree is required.
+
+   Fallback '${__DTC}' was also not in \${PATH} or is not executable.
+
+eod
+		exit 2
+	fi
+	DTC=${__DTC}
+fi
+
+
+# -----  cpp and dtc flags same as for linux source tree build of .dtb files,
+#        plus directories of the dtx file(s)
+
+dtx_path_1_dtc_include="-i `dirname ${dtx_file_1}`"
+
+dtx_path_2_dtc_include=""
+if (( ${cmd_diff} )) ; then
+	dtx_path_2_dtc_include="-i `dirname ${dtx_file_2}`"
+fi
+
+cpp_flags="\
+	-nostdinc                                  \
+	-I${srctree}/scripts/dtc/include-prefixes  \
+	-undef -D__DTS__"
+
+DTC="\
+	${DTC}                                     \
+	-i ${srctree}/scripts/dtc/include-prefixes \
+	-O dts -qq -f ${dtc_sort} ${annotate} -o -"
+
+
+# -----  do the diff or decompile
+
+if (( ${cmd_diff} )) ; then
+
+	diff ${diff_flags} ${diff_color} --label "${dtx_file_1}" --label "${dtx_file_2}" \
+		<(compile_to_dts "${dtx_file_1}" "${dtx_path_1_dtc_include}") \
+		<(compile_to_dts "${dtx_file_2}" "${dtx_path_2_dtc_include}")
+
+else
+
+	compile_to_dts "${dtx_file_1}" "${dtx_path_1_dtc_include}"
+
+fi