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, 165 insertions, 0 deletions

diff --git a/scripts/Makefile.host b/scripts/Makefile.host
new file mode 100644
index 000000000..c1dedf646
--- /dev/null
+++ b/scripts/Makefile.host
@@ -0,0 +1,165 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# LEX
+# ---------------------------------------------------------------------------
+quiet_cmd_flex = LEX     $@
+      cmd_flex = $(LEX) -o$@ -L $<
+
+$(obj)/%.lex.c: $(src)/%.l FORCE
+	$(call if_changed,flex)
+
+# YACC
+# ---------------------------------------------------------------------------
+quiet_cmd_bison = YACC    $(basename $@).[ch]
+      cmd_bison = $(YACC) -o $(basename $@).c --defines=$(basename $@).h -t -l $<
+
+$(obj)/%.tab.c $(obj)/%.tab.h: $(src)/%.y FORCE
+	$(call if_changed,bison)
+
+# ==========================================================================
+# Building binaries on the host system
+# Binaries are used during the compilation of the kernel, for example
+# to preprocess a data file.
+#
+# Both C and C++ are supported, but preferred language is C for such utilities.
+# Rust is also supported, but it may only be used in scenarios where a Rust
+# toolchain is required to be available (e.g. when  `CONFIG_RUST` is enabled).
+#
+# Sample syntax (see Documentation/kbuild/makefiles.rst for reference)
+# hostprogs := bin2hex
+# Will compile bin2hex.c and create an executable named bin2hex
+#
+# hostprogs     := lxdialog
+# lxdialog-objs := checklist.o lxdialog.o
+# Will compile lxdialog.c and checklist.c, and then link the executable
+# lxdialog, based on checklist.o and lxdialog.o
+#
+# hostprogs       := qconf
+# qconf-cxxobjs   := qconf.o
+# qconf-objs      := menu.o
+# Will compile qconf as a C++ program, and menu as a C program.
+# They are linked as C++ code to the executable qconf
+#
+# hostprogs   := target
+# target-rust := y
+# Will compile `target` as a Rust program, using `target.rs` as the crate root.
+# The crate may consist of several source files.
+
+# C code
+# Executables compiled from a single .c file
+host-csingle	:= $(foreach m,$(hostprogs), \
+			$(if $($(m)-objs)$($(m)-cxxobjs)$($(m)-rust),,$(m)))
+
+# C executables linked based on several .o files
+host-cmulti	:= $(foreach m,$(hostprogs),\
+		   $(if $($(m)-cxxobjs)$($(m)-rust),,$(if $($(m)-objs),$(m))))
+
+# Object (.o) files compiled from .c files
+host-cobjs	:= $(sort $(foreach m,$(hostprogs),$($(m)-objs)))
+
+# C++ code
+# C++ executables compiled from at least one .cc file
+# and zero or more .c files
+host-cxxmulti	:= $(foreach m,$(hostprogs),$(if $($(m)-cxxobjs),$(m)))
+
+# C++ Object (.o) files compiled from .cc files
+host-cxxobjs	:= $(sort $(foreach m,$(host-cxxmulti),$($(m)-cxxobjs)))
+
+# Rust code
+# Executables compiled from a single Rust crate (which may consist of
+# one or more .rs files)
+host-rust	:= $(foreach m,$(hostprogs),$(if $($(m)-rust),$(m)))
+
+host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
+host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
+host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))
+host-cxxmulti	:= $(addprefix $(obj)/,$(host-cxxmulti))
+host-cxxobjs	:= $(addprefix $(obj)/,$(host-cxxobjs))
+host-rust	:= $(addprefix $(obj)/,$(host-rust))
+
+#####
+# Handle options to gcc. Support building with separate output directory
+
+hostc_flags    = -Wp,-MMD,$(depfile) \
+                 $(KBUILD_HOSTCFLAGS) $(HOST_EXTRACFLAGS) \
+                 $(HOSTCFLAGS_$(target-stem).o)
+hostcxx_flags  = -Wp,-MMD,$(depfile) \
+                 $(KBUILD_HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
+                 $(HOSTCXXFLAGS_$(target-stem).o)
+
+# `--out-dir` is required to avoid temporaries being created by `rustc` in the
+# current working directory, which may be not accessible in the out-of-tree
+# modules case.
+hostrust_flags = --out-dir $(dir $@) --emit=dep-info=$(depfile) \
+		 -Clinker-flavor=gcc -Clinker=$(HOSTCC) \
+		 -Clink-args='$(call escsq,$(KBUILD_HOSTLDFLAGS))' \
+                 $(KBUILD_HOSTRUSTFLAGS) $(HOST_EXTRARUSTFLAGS) \
+                 $(HOSTRUSTFLAGS_$(target-stem))
+
+# $(obj) for including generated headers from checkin source files
+ifdef building_out_of_srctree
+hostc_flags   += -I $(obj)
+hostcxx_flags += -I $(obj)
+endif
+
+#####
+# Compile programs on the host
+
+# Create executable from a single .c file
+# host-csingle -> Executable
+quiet_cmd_host-csingle 	= HOSTCC  $@
+      cmd_host-csingle	= $(HOSTCC) $(hostc_flags) $(KBUILD_HOSTLDFLAGS) -o $@ $< \
+		$(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-csingle): $(obj)/%: $(obj)/%.c FORCE
+	$(call if_changed_dep,host-csingle)
+
+# Link an executable based on list of .o files, all plain c
+# host-cmulti -> executable
+quiet_cmd_host-cmulti	= HOSTLD  $@
+      cmd_host-cmulti	= $(HOSTCC) $(KBUILD_HOSTLDFLAGS) -o $@ \
+			  $(addprefix $(obj)/, $($(target-stem)-objs)) \
+			  $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-cmulti): FORCE
+	$(call if_changed,host-cmulti)
+$(call multi_depend, $(host-cmulti), , -objs)
+
+# Create .o file from a single .c file
+# host-cobjs -> .o
+quiet_cmd_host-cobjs	= HOSTCC  $@
+      cmd_host-cobjs	= $(HOSTCC) $(hostc_flags) -c -o $@ $<
+$(host-cobjs): $(obj)/%.o: $(obj)/%.c FORCE
+	$(call if_changed_dep,host-cobjs)
+
+# Link an executable based on list of .o files, a mixture of .c and .cc
+# host-cxxmulti -> executable
+quiet_cmd_host-cxxmulti	= HOSTLD  $@
+      cmd_host-cxxmulti	= $(HOSTCXX) $(KBUILD_HOSTLDFLAGS) -o $@ \
+			  $(foreach o,objs cxxobjs,\
+			  $(addprefix $(obj)/, $($(target-stem)-$(o)))) \
+			  $(KBUILD_HOSTLDLIBS) $(HOSTLDLIBS_$(target-stem))
+$(host-cxxmulti): FORCE
+	$(call if_changed,host-cxxmulti)
+$(call multi_depend, $(host-cxxmulti), , -objs -cxxobjs)
+
+# Create .o file from a single .cc (C++) file
+quiet_cmd_host-cxxobjs	= HOSTCXX $@
+      cmd_host-cxxobjs	= $(HOSTCXX) $(hostcxx_flags) -c -o $@ $<
+$(host-cxxobjs): $(obj)/%.o: $(obj)/%.cc FORCE
+	$(call if_changed_dep,host-cxxobjs)
+
+# Create executable from a single Rust crate (which may consist of
+# one or more `.rs` files)
+# host-rust -> Executable
+quiet_cmd_host-rust	= HOSTRUSTC $@
+      cmd_host-rust	= \
+	$(HOSTRUSTC) $(hostrust_flags) --emit=link=$@ $<
+$(host-rust): $(obj)/%: $(src)/%.rs FORCE
+	+$(call if_changed_dep,host-rust)
+
+targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
+	   $(host-cxxmulti) $(host-cxxobjs) $(host-rust)
+
+# %.lex.o <- %.lex.c <- %.l
+# %.tab.o <- %.tab.[ch] <- %.y
+targets += $(call intermediate_targets, .lex.o, .lex.c) \
+           $(call intermediate_targets, .tab.o, .tab.c .tab.h)