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, 226 insertions, 0 deletions

diff --git a/scripts/package/kernel.spec b/scripts/package/kernel.spec
new file mode 100644
index 000000000..46e80970f
--- /dev/null
+++ b/scripts/package/kernel.spec
@@ -0,0 +1,226 @@
+# _arch is undefined if /usr/lib/rpm/platform/*/macros was not included.
+%{!?_arch: %define _arch dummy}
+%{!?make: %define make make}
+%define makeflags %{?_smp_mflags} ARCH=%{ARCH}
+
+Name: kernel
+Summary: The Linux Kernel
+Version: %(echo %{KERNELRELEASE} | sed -e 's/-/_/g')
+Release: %{pkg_release}%{?dist}
+License: GPL
+Group: System Environment/Kernel
+Vendor: The Linux Community
+URL: https://www.kernel.org
+Source0: linux.tar.gz
+Source1: config
+Source2: diff.patch
+Provides: kernel-%{KERNELRELEASE}
+BuildRequires: bc binutils bison dwarves
+BuildRequires: (elfutils-devel or libdw-devel)
+BuildRequires: (elfutils-libelf-devel or libelf-devel) flex
+BuildRequires: gcc make openssl openssl-devel perl python3 rsync
+
+%description
+The Linux Kernel, the operating system core itself
+
+%package headers
+Summary: Header files for the Linux kernel for use by glibc
+Group: Development/System
+Obsoletes: kernel-headers < %{version}
+Provides: kernel-headers = %{version}
+%description headers
+Kernel-headers includes the C header files that specify the interface
+between the Linux kernel and userspace libraries and programs.  The
+header files define structures and constants that are needed for
+building most standard programs and are also needed for rebuilding the
+glibc package.
+
+%if %{with_devel}
+%package devel
+Summary: Development package for building kernel modules to match the %{version} kernel
+Group: System Environment/Kernel
+AutoReqProv: no
+%description -n kernel-devel
+This package provides kernel headers and makefiles sufficient to build modules
+against the %{version} kernel package.
+%endif
+
+%if %{with_debuginfo_manual}
+%package debuginfo
+Summary: Debug information package for the Linux kernel
+Group: Development/Debug
+AutoReq: 0
+AutoProv: 1
+%description debuginfo
+This package provides debug information for the kernel image and modules from the
+%{version} package.
+%define install_mod_strip 1
+%endif
+
+%if %{with_debuginfo_rpm}
+# list of debuginfo-related options taken from distribution kernel.spec
+# files
+%undefine _include_minidebuginfo
+%undefine _find_debuginfo_dwz_opts
+%undefine _unique_build_ids
+%undefine _unique_debug_names
+%undefine _unique_debug_srcs
+%undefine _debugsource_packages
+%undefine _debuginfo_subpackages
+
+# Preserve .BTF and .BTF.base sections in kernel modules during debuginfo
+# stripping. find-debuginfo.sh uses eu-strip which removes non-allocated ELF
+# sections like .BTF by default. .BTF.base is required for BTF distillation
+# support; without it, module BTF validation fails.
+%global with_keep_section %(%{__find_debuginfo} --help 2>&1 | grep -c keep-section)
+%if %{with_keep_section}
+%global _find_debuginfo_opts -r --keep-section .BTF --keep-section .BTF.base
+%else
+%global _find_debuginfo_opts -r
+%endif
+
+%global _missing_build_ids_terminate_build 1
+%global _no_recompute_build_ids 1
+%{debug_package}
+
+# later, we make all modules executable so that find-debuginfo.sh strips
+# them up. but they don't actually need to be executable, so remove the
+# executable bit, taking care to do it _after_ find-debuginfo.sh has run
+%define __spec_install_post \
+	%{?__debug_package:%{__debug_install_post}} \
+	%{__arch_install_post} \
+	%{__os_install_post} \
+	find %{buildroot}/lib/modules/%{KERNELRELEASE} -name "*.ko" -type f \\\
+		| xargs --no-run-if-empty chmod u-x
+%else
+%define __spec_install_post /usr/lib/rpm/brp-compress || :
+%endif
+# some (but not all) versions of rpmbuild emit %%debug_package with
+# %%install. since we've already emitted it manually, that would cause
+# a package redefinition error. ensure that doesn't happen
+%define debug_package %{nil}
+
+%prep
+%setup -q -n linux
+cp %{SOURCE1} .config
+patch -p1 < %{SOURCE2}
+
+%build
+%{make} %{makeflags} KERNELRELEASE=%{KERNELRELEASE} KBUILD_BUILD_VERSION=%{release}
+
+%install
+mkdir -p %{buildroot}/lib/modules/%{KERNELRELEASE}
+cp $(%{make} %{makeflags} -s image_name) %{buildroot}/lib/modules/%{KERNELRELEASE}/vmlinuz
+# DEPMOD=true makes depmod no-op. We do not package depmod-generated files.
+%{make} %{makeflags} INSTALL_MOD_PATH=%{buildroot} %{?install_mod_strip:INSTALL_MOD_STRIP=1} DEPMOD=true modules_install
+%{make} %{makeflags} INSTALL_HDR_PATH=%{buildroot}/usr headers_install
+cp System.map %{buildroot}/lib/modules/%{KERNELRELEASE}
+cp .config %{buildroot}/lib/modules/%{KERNELRELEASE}/config
+if %{make} %{makeflags} run-command KBUILD_RUN_COMMAND='test -d ${srctree}/arch/${SRCARCH}/boot/dts' 2>/dev/null; then
+	%{make} %{makeflags} INSTALL_DTBS_PATH=%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb dtbs_install
+fi
+ln -fns /usr/src/kernels/%{KERNELRELEASE} %{buildroot}/lib/modules/%{KERNELRELEASE}/build
+%if %{with_devel}
+%{make} %{makeflags} run-command KBUILD_RUN_COMMAND='${srctree}/scripts/package/install-extmod-build %{buildroot}/usr/src/kernels/%{KERNELRELEASE}'
+%endif
+
+{
+	echo "/lib/modules/%{KERNELRELEASE}"
+
+	for x in alias alias.bin builtin.alias.bin builtin.bin dep dep.bin \
+				devname softdep symbols symbols.bin weakdep; do
+		echo "%ghost /lib/modules/%{KERNELRELEASE}/modules.${x}"
+	done
+
+	for x in System.map config vmlinuz; do
+		echo "%ghost /boot/${x}-%{KERNELRELEASE}"
+	done
+
+	if [ -d "%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb" ];then
+		find "%{buildroot}/lib/modules/%{KERNELRELEASE}/dtb" -printf "%%%ghost /boot/dtb-%{KERNELRELEASE}/%%P\n"
+	fi
+
+	echo "%exclude /lib/modules/%{KERNELRELEASE}/build"
+} > %{buildroot}/kernel.list
+
+%if 0%{with_debuginfo_manual}%{with_debuginfo_rpm} > 0
+# copying vmlinux directly to the debug directory means it will not get
+# stripped (but its source paths will still be collected + fixed up)
+mkdir -p %{buildroot}/usr/lib/debug/lib/modules/%{KERNELRELEASE}
+cp vmlinux %{buildroot}/usr/lib/debug/lib/modules/%{KERNELRELEASE}
+%endif
+
+%if %{with_debuginfo_rpm}
+# make modules executable so that find-debuginfo.sh strips them. this
+# will be undone later in %%__spec_install_post
+find %{buildroot}/lib/modules/%{KERNELRELEASE} -name "*.ko" -type f \
+	| xargs --no-run-if-empty chmod u+x
+%endif
+
+%if %{with_debuginfo_manual}
+echo /usr/lib/debug/lib/modules/%{KERNELRELEASE}/vmlinux > %{buildroot}/debuginfo.list
+while read -r mod; do
+	mod="${mod%.o}.ko"
+	dbg="%{buildroot}/usr/lib/debug/lib/modules/%{KERNELRELEASE}/kernel/${mod}"
+	buildid=$("${READELF:-readelf}" -n "${mod}" | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+	link="%{buildroot}/usr/lib/debug/.build-id/${buildid}.debug"
+
+	mkdir -p "${dbg%/*}" "${link%/*}"
+	"${OBJCOPY:-objcopy}" --only-keep-debug "${mod}" "${dbg}"
+	ln -sf --relative "${dbg}" "${link}"
+
+	echo "${dbg#%{buildroot}}" >> %{buildroot}/debuginfo.list
+	echo "${link#%{buildroot}}" >> %{buildroot}/debuginfo.list
+done < modules.order
+%endif
+
+%clean
+rm -rf %{buildroot}
+%if %{with_debuginfo_rpm}
+rm -f debugfiles.list debuglinks.list debugsourcefiles.list debugsources.list \
+	elfbins.list
+%endif
+
+%post
+if [ -x /usr/bin/kernel-install ]; then
+	/usr/bin/kernel-install add %{KERNELRELEASE} /lib/modules/%{KERNELRELEASE}/vmlinuz
+fi
+for file in vmlinuz System.map config; do
+	if ! cmp --silent "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"; then
+		cp "/lib/modules/%{KERNELRELEASE}/${file}" "/boot/${file}-%{KERNELRELEASE}"
+	fi
+done
+if [ -d "/lib/modules/%{KERNELRELEASE}/dtb" ] && \
+   ! diff -rq "/lib/modules/%{KERNELRELEASE}/dtb" "/boot/dtb-%{KERNELRELEASE}" >/dev/null 2>&1; then
+	rm -rf "/boot/dtb-%{KERNELRELEASE}"
+	cp -r "/lib/modules/%{KERNELRELEASE}/dtb" "/boot/dtb-%{KERNELRELEASE}"
+fi
+if [ ! -e "/lib/modules/%{KERNELRELEASE}/modules.dep" ]; then
+	/usr/sbin/depmod %{KERNELRELEASE}
+fi
+
+%preun
+if [ -x /usr/bin/kernel-install ]; then
+kernel-install remove %{KERNELRELEASE}
+fi
+
+%files -f %{buildroot}/kernel.list
+%defattr (-, root, root)
+%exclude /kernel.list
+
+%files headers
+%defattr (-, root, root)
+/usr/include
+
+%if %{with_devel}
+%files devel
+%defattr (-, root, root)
+/usr/src/kernels/%{KERNELRELEASE}
+/lib/modules/%{KERNELRELEASE}/build
+%endif
+
+%if %{with_debuginfo_manual}
+%files -f %{buildroot}/debuginfo.list debuginfo
+%defattr (-, root, root)
+%exclude /debuginfo.list
+%endif