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, 507 insertions, 0 deletions

diff --git a/tools/lib/python/feat/parse_features.py b/tools/lib/python/feat/parse_features.py
new file mode 100755
index 000000000..41a51d9d6
--- /dev/null
+++ b/tools/lib/python/feat/parse_features.py
@@ -0,0 +1,507 @@
+#!/usr/bin/env python3
+# pylint: disable=R0902,R0911,R0912,R0914,R0915
+# Copyright(c) 2025: Mauro Carvalho Chehab <mchehab@kernel.org>.
+# SPDX-License-Identifier: GPL-2.0
+
+
+"""
+Library to parse the Linux Feature files and produce a ReST book.
+"""
+
+import os
+import re
+import sys
+
+from glob import iglob
+
+
+class ParseFeature:
+    """
+    Parses Documentation/features, allowing to generate ReST documentation
+    from it.
+    """
+
+    #: feature header string.
+    h_name = "Feature"
+
+    #: Kernel config header string.
+    h_kconfig = "Kconfig"
+
+    #: description header string.
+    h_description = "Description"
+
+    #: subsystem header string.
+    h_subsys = "Subsystem"
+
+    #: status header string.
+    h_status = "Status"
+
+    #: architecture header string.
+    h_arch = "Architecture"
+
+    #: Sort order for status. Others will be mapped at the end.
+    status_map = {
+        "ok":   0,
+        "TODO": 1,
+        "N/A":  2,
+        # The only missing status is "..", which was mapped as "---",
+        # as this is an special ReST cell value. Let it get the
+        # default order (99).
+    }
+
+    def __init__(self, prefix, debug=0, enable_fname=False):
+        """
+        Sets internal variables.
+        """
+
+        self.prefix = prefix
+        self.debug = debug
+        self.enable_fname = enable_fname
+
+        self.data = {}
+
+        # Initial maximum values use just the headers
+        self.max_size_name = len(self.h_name)
+        self.max_size_kconfig = len(self.h_kconfig)
+        self.max_size_description = len(self.h_description)
+        self.max_size_desc_word = 0
+        self.max_size_subsys = len(self.h_subsys)
+        self.max_size_status = len(self.h_status)
+        self.max_size_arch = len(self.h_arch)
+        self.max_size_arch_with_header = self.max_size_arch + self.max_size_arch
+        self.description_size = 1
+
+        self.msg = ""
+
+    def emit(self, msg="", end="\n"):
+        """Helper function to append a new message for feature output."""
+
+        self.msg += msg + end
+
+    def parse_error(self, fname, ln, msg, data=None):
+        """
+        Displays an error message, printing file name and line.
+        """
+
+        if ln:
+            fname += f"#{ln}"
+
+        print(f"Warning: file {fname}: {msg}", file=sys.stderr, end="")
+
+        if data:
+            data = data.rstrip()
+            print(f":\n\t{data}", file=sys.stderr)
+        else:
+            print("", file=sys.stderr)
+
+    def parse_feat_file(self, fname):
+        """Parses a single arch-support.txt feature file."""
+
+        if os.path.isdir(fname):
+            return
+
+        base = os.path.basename(fname)
+
+        if base != "arch-support.txt":
+            if self.debug:
+                print(f"ignoring {fname}", file=sys.stderr)
+            return
+
+        subsys = os.path.dirname(fname).split("/")[-2]
+        self.max_size_subsys = max(self.max_size_subsys, len(subsys))
+
+        feature_name = ""
+        kconfig = ""
+        description = ""
+        comments = ""
+        arch_table = {}
+
+        if self.debug > 1:
+            print(f"Opening {fname}", file=sys.stderr)
+
+        if self.enable_fname:
+            full_fname = os.path.abspath(fname)
+            self.emit(f".. FILE {full_fname}")
+
+        with open(fname, encoding="utf-8") as f:
+            for ln, line in enumerate(f, start=1):
+                line = line.strip()
+
+                match = re.match(r"^\#\s+Feature\s+name:\s*(.*\S)", line)
+                if match:
+                    feature_name = match.group(1)
+
+                    self.max_size_name = max(self.max_size_name,
+                                             len(feature_name))
+                    continue
+
+                match = re.match(r"^\#\s+Kconfig:\s*(.*\S)", line)
+                if match:
+                    kconfig = match.group(1)
+
+                    self.max_size_kconfig = max(self.max_size_kconfig,
+                                                len(kconfig))
+                    continue
+
+                match = re.match(r"^\#\s+description:\s*(.*\S)", line)
+                if match:
+                    description = match.group(1)
+
+                    self.max_size_description = max(self.max_size_description,
+                                                    len(description))
+
+                    words = re.split(r"\s+", line)[1:]
+                    for word in words:
+                        self.max_size_desc_word = max(self.max_size_desc_word,
+                                                        len(word))
+
+                    continue
+
+                if re.search(r"^\\s*$", line):
+                    continue
+
+                if re.match(r"^\s*\-+\s*$", line):
+                    continue
+
+                if re.search(r"^\s*\|\s*arch\s*\|\s*status\s*\|\s*$", line):
+                    continue
+
+                match = re.match(r"^\#\s*(.*)$", line)
+                if match:
+                    comments += match.group(1)
+                    continue
+
+                match = re.match(r"^\s*\|\s*(\S+):\s*\|\s*(\S+)\s*\|\s*$", line)
+                if match:
+                    arch = match.group(1)
+                    status = match.group(2)
+
+                    self.max_size_status = max(self.max_size_status,
+                                               len(status))
+                    self.max_size_arch = max(self.max_size_arch, len(arch))
+
+                    if status == "..":
+                        status = "---"
+
+                    arch_table[arch] = status
+
+                    continue
+
+                self.parse_error(fname, ln, "Line is invalid", line)
+
+        if not feature_name:
+            self.parse_error(fname, 0, "Feature name not found")
+            return
+        if not subsys:
+            self.parse_error(fname, 0, "Subsystem not found")
+            return
+        if not kconfig:
+            self.parse_error(fname, 0, "Kconfig not found")
+            return
+        if not description:
+            self.parse_error(fname, 0, "Description not found")
+            return
+        if not arch_table:
+            self.parse_error(fname, 0, "Architecture table not found")
+            return
+
+        self.data[feature_name] = {
+            "where": fname,
+            "subsys": subsys,
+            "kconfig": kconfig,
+            "description": description,
+            "comments": comments,
+            "table": arch_table,
+        }
+
+        self.max_size_arch_with_header = self.max_size_arch + len(self.h_arch)
+
+    def parse(self):
+        """Parses all arch-support.txt feature files inside self.prefix."""
+
+        path = os.path.expanduser(self.prefix)
+
+        if self.debug > 2:
+            print(f"Running parser for {path}")
+
+        example_path = os.path.join(path, "arch-support.txt")
+
+        for fname in iglob(os.path.join(path, "**"), recursive=True):
+            if fname != example_path:
+                self.parse_feat_file(fname)
+
+        return self.data
+
+    def output_arch_table(self, arch, feat=None):
+        """
+        Output feature(s) for a given architecture.
+        """
+
+        title = f"Feature status on {arch} architecture"
+
+        self.emit("=" * len(title))
+        self.emit(title)
+        self.emit("=" * len(title))
+        self.emit()
+
+        self.emit("=" * self.max_size_subsys + "  ", end="")
+        self.emit("=" * self.max_size_name + "  ", end="")
+        self.emit("=" * self.max_size_kconfig + "  ", end="")
+        self.emit("=" * self.max_size_status + "  ", end="")
+        self.emit("=" * self.max_size_description)
+
+        self.emit(f"{self.h_subsys:<{self.max_size_subsys}}  ", end="")
+        self.emit(f"{self.h_name:<{self.max_size_name}}  ", end="")
+        self.emit(f"{self.h_kconfig:<{self.max_size_kconfig}}  ", end="")
+        self.emit(f"{self.h_status:<{self.max_size_status}}  ", end="")
+        self.emit(f"{self.h_description:<{self.max_size_description}}")
+
+        self.emit("=" * self.max_size_subsys + "  ", end="")
+        self.emit("=" * self.max_size_name + "  ", end="")
+        self.emit("=" * self.max_size_kconfig + "  ", end="")
+        self.emit("=" * self.max_size_status + "  ", end="")
+        self.emit("=" * self.max_size_description)
+
+        sorted_features = sorted(self.data.keys(),
+                                 key=lambda x: (self.data[x]["subsys"],
+                                                x.lower()))
+
+        for name in sorted_features:
+            if feat and name != feat:
+                continue
+
+            arch_table = self.data[name]["table"]
+
+            if not arch in arch_table:
+                continue
+
+            self.emit(f"{self.data[name]['subsys']:<{self.max_size_subsys}}  ",
+                  end="")
+            self.emit(f"{name:<{self.max_size_name}}  ", end="")
+            self.emit(f"{self.data[name]['kconfig']:<{self.max_size_kconfig}}  ",
+                  end="")
+            self.emit(f"{arch_table[arch]:<{self.max_size_status}}  ",
+                  end="")
+            self.emit(f"{self.data[name]['description']}")
+
+        self.emit("=" * self.max_size_subsys + "  ", end="")
+        self.emit("=" * self.max_size_name + "  ", end="")
+        self.emit("=" * self.max_size_kconfig + "  ", end="")
+        self.emit("=" * self.max_size_status + "  ", end="")
+        self.emit("=" * self.max_size_description)
+
+        return self.msg
+
+    def output_feature(self, feat):
+        """
+        Output a feature on all architectures.
+        """
+
+        title = f"Feature {feat}"
+
+        self.emit("=" * len(title))
+        self.emit(title)
+        self.emit("=" * len(title))
+        self.emit()
+
+        if not feat in self.data:
+            return
+
+        if self.data[feat]["subsys"]:
+            self.emit(f":Subsystem: {self.data[feat]['subsys']}")
+        if self.data[feat]["kconfig"]:
+            self.emit(f":Kconfig: {self.data[feat]['kconfig']}")
+
+        desc = self.data[feat]["description"]
+        desc = desc[0].upper() + desc[1:]
+        desc = desc.rstrip(". \t")
+        self.emit(f"\n{desc}.\n")
+
+        com = self.data[feat]["comments"].strip()
+        if com:
+            self.emit("Comments")
+            self.emit("--------")
+            self.emit(f"\n{com}\n")
+
+        self.emit("=" * self.max_size_arch + "  ", end="")
+        self.emit("=" * self.max_size_status)
+
+        self.emit(f"{self.h_arch:<{self.max_size_arch}}  ", end="")
+        self.emit(f"{self.h_status:<{self.max_size_status}}")
+
+        self.emit("=" * self.max_size_arch + "  ", end="")
+        self.emit("=" * self.max_size_status)
+
+        arch_table = self.data[feat]["table"]
+        for arch in sorted(arch_table.keys()):
+            self.emit(f"{arch:<{self.max_size_arch}}  ", end="")
+            self.emit(f"{arch_table[arch]:<{self.max_size_status}}")
+
+        self.emit("=" * self.max_size_arch + "  ", end="")
+        self.emit("=" * self.max_size_status)
+
+        return self.msg
+
+    def matrix_lines(self, desc_size, max_size_status, header):
+        """
+        Helper function to split element tables at the output matrix.
+        """
+
+        if header:
+            ln_marker = "="
+        else:
+            ln_marker = "-"
+
+        self.emit("+" + ln_marker * self.max_size_name + "+", end="")
+        self.emit(ln_marker * desc_size, end="")
+        self.emit("+" + ln_marker * max_size_status + "+")
+
+    def output_matrix(self):
+        """
+        Generates a set of tables, groped by subsystem, containing
+        what's the feature state on each architecture.
+        """
+
+        title = "Feature status on all architectures"
+
+        self.emit("=" * len(title))
+        self.emit(title)
+        self.emit("=" * len(title))
+        self.emit()
+
+        desc_title = f"{self.h_kconfig} / {self.h_description}"
+
+        desc_size = self.max_size_kconfig + 4
+        if not self.description_size:
+            desc_size = max(self.max_size_description, desc_size)
+        else:
+            desc_size = max(self.description_size, desc_size)
+
+        desc_size = max(self.max_size_desc_word, desc_size, len(desc_title))
+
+        notcompat = "Not compatible"
+        self.max_size_status = max(self.max_size_status, len(notcompat))
+
+        min_status_size = self.max_size_status + self.max_size_arch + 4
+        max_size_status = max(min_status_size, self.max_size_status)
+
+        h_status_per_arch = "Status per architecture"
+        max_size_status = max(max_size_status, len(h_status_per_arch))
+
+        cur_subsys = None
+        for name in sorted(self.data.keys(),
+                           key=lambda x: (self.data[x]["subsys"], x.lower())):
+            if not cur_subsys or cur_subsys != self.data[name]["subsys"]:
+                if cur_subsys:
+                    self.emit()
+
+                cur_subsys = self.data[name]["subsys"]
+
+                title = f"Subsystem: {cur_subsys}"
+                self.emit(title)
+                self.emit("=" * len(title))
+                self.emit()
+
+                self.matrix_lines(desc_size, max_size_status, 0)
+
+                self.emit(f"|{self.h_name:<{self.max_size_name}}", end="")
+                self.emit(f"|{desc_title:<{desc_size}}", end="")
+                self.emit(f"|{h_status_per_arch:<{max_size_status}}|")
+
+                self.matrix_lines(desc_size, max_size_status, 1)
+
+            lines = []
+            descs = []
+            cur_status = ""
+            line = ""
+
+            arch_table = sorted(self.data[name]["table"].items(),
+                                key=lambda x: (self.status_map.get(x[1], 99),
+                                               x[0].lower()))
+
+            for arch, status in arch_table:
+                if status == "---":
+                    status = notcompat
+
+                if status != cur_status:
+                    if line != "":
+                        lines.append(line)
+                        line = ""
+                    line = f"- **{status}**: {arch}"
+                elif len(line) + len(arch) + 2 < max_size_status:
+                    line += f", {arch}"
+                else:
+                    lines.append(line)
+                    line = f"  {arch}"
+                cur_status = status
+
+            if line != "":
+                lines.append(line)
+
+            description = self.data[name]["description"]
+            while len(description) > desc_size:
+                desc_line = description[:desc_size]
+
+                last_space = desc_line.rfind(" ")
+                if last_space != -1:
+                    desc_line = desc_line[:last_space]
+                    descs.append(desc_line)
+                    description = description[last_space + 1:]
+                else:
+                    desc_line = desc_line[:-1]
+                    descs.append(desc_line + "\\")
+                    description = description[len(desc_line):]
+
+            if description:
+                descs.append(description)
+
+            while len(lines) < 2 + len(descs):
+                lines.append("")
+
+            for ln, line in enumerate(lines):
+                col = ["", ""]
+
+                if not ln:
+                    col[0] = name
+                    col[1] = f"``{self.data[name]['kconfig']}``"
+                else:
+                    if ln >= 2 and descs:
+                        col[1] = descs.pop(0)
+
+                self.emit(f"|{col[0]:<{self.max_size_name}}", end="")
+                self.emit(f"|{col[1]:<{desc_size}}", end="")
+                self.emit(f"|{line:<{max_size_status}}|")
+
+            self.matrix_lines(desc_size, max_size_status, 0)
+
+        return self.msg
+
+    def list_arch_features(self, arch, feat):
+        """
+        Print a matrix of kernel feature support for the chosen architecture.
+        """
+        self.emit("#")
+        self.emit(f"# Kernel feature support matrix of the '{arch}' architecture:")
+        self.emit("#")
+
+        # Sort by subsystem, then by feature name (case‑insensitive)
+        for name in sorted(self.data.keys(),
+                           key=lambda n: (self.data[n]["subsys"].lower(),
+                                          n.lower())):
+            if feat and name != feat:
+                continue
+
+            feature = self.data[name]
+            arch_table = feature["table"]
+            status = arch_table.get(arch, "")
+            status = " " * ((4 - len(status)) // 2) + status
+
+            self.emit(f"{feature['subsys']:>{self.max_size_subsys + 1}}/ ",
+                      end="")
+            self.emit(f"{name:<{self.max_size_name}}: ", end="")
+            self.emit(f"{status:<5}|   ", end="")
+            self.emit(f"{feature['kconfig']:>{self.max_size_kconfig}} ",
+                      end="")
+            self.emit(f"#  {feature['description']}")
+
+        return self.msg