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, 123 insertions, 0 deletions

diff --git a/Documentation/sphinx/parser_yaml.py b/Documentation/sphinx/parser_yaml.py
new file mode 100755
index 000000000..634d84a20
--- /dev/null
+++ b/Documentation/sphinx/parser_yaml.py
@@ -0,0 +1,123 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright 2025 Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
+
+"""
+Sphinx extension for processing YAML files
+"""
+
+import os
+import re
+import sys
+
+from pprint import pformat
+
+from docutils import statemachine
+from docutils.parsers.rst import Parser as RSTParser
+from docutils.parsers.rst import states
+from docutils.statemachine import ViewList
+
+from sphinx.util import logging
+from sphinx.parsers import Parser
+
+srctree = os.path.abspath(os.environ["srctree"])
+sys.path.insert(0, os.path.join(srctree, "tools/net/ynl/pyynl/lib"))
+
+from doc_generator import YnlDocGenerator        # pylint: disable=C0413
+
+logger = logging.getLogger(__name__)
+
+class YamlParser(Parser):
+    """
+    Kernel parser for YAML files.
+
+    This is a simple sphinx.Parser to handle yaml files inside the
+    Kernel tree that will be part of the built documentation.
+
+    The actual parser function is not contained here: the code was
+    written in a way that parsing yaml for different subsystems
+    can be done from a single dispatcher.
+
+    All it takes to have parse YAML patches is to have an import line:
+
+            from some_parser_code import NewYamlGenerator
+
+    To this module. Then add an instance of the parser with:
+
+            new_parser = NewYamlGenerator()
+
+    and add a logic inside parse() to handle it based on the path,
+    like this:
+
+            if "/foo" in fname:
+                msg = self.new_parser.parse_yaml_file(fname)
+    """
+
+    supported = ('yaml', )
+
+    netlink_parser = YnlDocGenerator()
+
+    re_lineno = re.compile(r"\.\. LINENO ([0-9]+)$")
+
+    tab_width = 8
+
+    def rst_parse(self, inputstring, document, msg):
+        """
+        Receives a ReST content that was previously converted by the
+        YAML parser, adding it to the document tree.
+        """
+
+        self.setup_parse(inputstring, document)
+
+        result = ViewList()
+
+        self.statemachine = states.RSTStateMachine(state_classes=states.state_classes,
+                                                   initial_state='Body',
+                                                   debug=document.reporter.debug_flag)
+
+        try:
+            # Parse message with RSTParser
+            lineoffset = 0;
+
+            lines = statemachine.string2lines(msg, self.tab_width,
+                                              convert_whitespace=True)
+
+            for line in lines:
+                match = self.re_lineno.match(line)
+                if match:
+                    lineoffset = int(match.group(1))
+                    continue
+
+                result.append(line, document.current_source, lineoffset)
+
+            self.statemachine.run(result, document)
+
+        except Exception as e:
+            document.reporter.error("YAML parsing error: %s" % pformat(e))
+
+        self.finish_parse()
+
+    # Overrides docutils.parsers.Parser. See sphinx.parsers.RSTParser
+    def parse(self, inputstring, document):
+        """Check if a YAML is meant to be parsed."""
+
+        fname = document.current_source
+
+        # Handle netlink yaml specs
+        if "/netlink/specs/" in fname:
+            msg = self.netlink_parser.parse_yaml_file(fname)
+            self.rst_parse(inputstring, document, msg)
+
+        # All other yaml files are ignored
+
+def setup(app):
+    """Setup function for the Sphinx extension."""
+
+    # Add YAML parser
+    app.add_source_parser(YamlParser)
+    app.add_source_suffix('.yaml', 'yaml')
+
+    return {
+        'version': '1.0',
+        'parallel_read_safe': True,
+        'parallel_write_safe': True,
+    }