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, 52 insertions, 0 deletions

diff --git a/tools/scripts/Makefile.arch b/tools/scripts/Makefile.arch
new file mode 100644
index 000000000..ed5f008d4
--- /dev/null
+++ b/tools/scripts/Makefile.arch
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: GPL-2.0
+HOSTARCH := $(shell uname -m | sed -e s/i.86/x86/ -e s/x86_64/x86/ \
+                                  -e s/sun4u/sparc/ -e s/sparc64/sparc/ \
+                                  -e /arm64/!s/arm.*/arm/ -e s/sa110/arm/ \
+                                  -e s/s390x/s390/ -e s/parisc64/parisc/ \
+                                  -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
+                                  -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ \
+                                  -e s/riscv.*/riscv/ -e s/loongarch.*/loongarch/)
+
+ifeq ($(strip $(ARCH)),)
+override ARCH := $(HOSTARCH)
+endif
+
+SRCARCH := $(ARCH)
+
+# Additional ARCH settings for x86
+ifeq ($(ARCH),i386)
+        SRCARCH := x86
+endif
+ifeq ($(ARCH),x86_64)
+        SRCARCH := x86
+endif
+
+# Additional ARCH settings for sparc
+ifeq ($(ARCH),sparc32)
+       SRCARCH := sparc
+endif
+ifeq ($(ARCH),sparc64)
+       SRCARCH := sparc
+endif
+
+# Additional ARCH settings for loongarch
+ifeq ($(ARCH),loongarch32)
+       SRCARCH := loongarch
+endif
+
+ifeq ($(ARCH),loongarch64)
+       SRCARCH := loongarch
+endif
+
+# Probe for __LP64__ only when the compiler is installed: this runs at
+# parse time for every target, including ones that never compile, e.g.
+# install-build-deps, and would otherwise spew "gcc: not found" when the
+# compiler is not yet installed. Only the first word of CC is consulted,
+# as CC may carry arguments, e.g. 'ccache gcc'. When the guard fails it
+# prints nothing, leaving LP64 unset, as if the probe had failed.
+LP64 := $(shell if command -v $(firstword ${CC}) >/dev/null 2>&1; then echo __LP64__ | ${CC} ${CFLAGS} -E -x c -; fi | tail -n 1)
+ifeq ($(LP64), 1)
+  IS_64_BIT := 1
+else
+  IS_64_BIT := 0
+endif