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, 38 insertions, 0 deletions

diff --git a/scripts/package/gen-diff-patch b/scripts/package/gen-diff-patch
new file mode 100755
index 000000000..f272f7770
--- /dev/null
+++ b/scripts/package/gen-diff-patch
@@ -0,0 +1,38 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+
+set -eu
+
+diff_patch=$1
+
+mkdir -p "$(dirname "${diff_patch}")"
+
+git -C "${srctree:-.}" diff HEAD > "${diff_patch}"
+
+if [ ! -s "${diff_patch}" ] ||
+   [ -z "$(git -C "${srctree:-.}" ls-files --other --exclude-standard | head -n1)" ]; then
+	exit
+fi
+
+# The source tarball, which is generated by 'git archive', contains everything
+# you committed in the repository. If you have local diff ('git diff HEAD'),
+# it will go into ${diff_patch}. If untracked files are remaining, the resulting
+# source package may not be correct.
+#
+# Examples:
+#  - You modified a source file to add #include "new-header.h"
+#    but forgot to add new-header.h
+#  - You modified a Makefile to add 'obj-$(CONFIG_FOO) += new-dirver.o'
+#    but you forgot to add new-driver.c
+#
+# You need to commit them, or at least stage them by 'git add'.
+#
+# This script does not take care of untracked files because doing so would
+# introduce additional complexity. Instead, print a warning message here if
+# untracked files are found.
+# If all untracked files are just garbage, you can ignore this warning.
+echo >&2 "============================ WARNING ============================"
+echo >&2 "Your working tree has diff from HEAD, and also untracked file(s)."
+echo >&2 "Please make sure you did 'git add' for all new files you need in"
+echo >&2 "the source package."
+echo >&2 "================================================================="