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, 131 insertions, 0 deletions

diff --git a/scripts/macro_checker.py b/scripts/macro_checker.py
new file mode 100755
index 000000000..ba550982e
--- /dev/null
+++ b/scripts/macro_checker.py
@@ -0,0 +1,131 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: GPL-2.0
+# Author: Julian Sun <sunjunchao2870@gmail.com>
+
+""" Find macro definitions with unused parameters. """
+
+import argparse
+import os
+import re
+
+parser = argparse.ArgumentParser()
+
+parser.add_argument("path", type=str, help="The file or dir path that needs check")
+parser.add_argument("-v", "--verbose", action="store_true",
+                    help="Check conditional macros, but may lead to more false positives")
+args = parser.parse_args()
+
+macro_pattern = r"#define\s+(\w+)\(([^)]*)\)"
+# below vars were used to reduce false positives
+fp_patterns = [r"\s*do\s*\{\s*\}\s*while\s*\(\s*0\s*\)",
+               r"\(?0\)?", r"\(?1\)?"]
+correct_macros = []
+cond_compile_mark = "#if"
+cond_compile_end = "#endif"
+
+def check_macro(macro_line, report):
+    match = re.match(macro_pattern, macro_line)
+    if match:
+        macro_def = re.sub(macro_pattern, '', macro_line)
+        identifier = match.group(1)
+        content = match.group(2)
+        arguments = [item.strip() for item in content.split(',') if item.strip()]
+
+        macro_def = macro_def.strip()
+        if not macro_def:
+            return
+        # used to reduce false positives, like #define endfor_nexthops(rt) }
+        if len(macro_def) == 1:
+            return
+
+        for fp_pattern in fp_patterns:
+            if (re.match(fp_pattern, macro_def)):
+                return
+
+        for arg in arguments:
+            # used to reduce false positives
+            if "..." in arg:
+                return
+        for arg in arguments:
+            if not arg in macro_def and report == False:
+                return
+            # if there is a correct macro with the same name, do not report it.
+            if not arg in macro_def and identifier not in correct_macros:
+                print(f"Argument {arg} is not used in function-line macro {identifier}")
+                return
+
+        correct_macros.append(identifier)
+
+
+# remove comment and whitespace
+def macro_strip(macro):
+    comment_pattern1 = r"\/\/*"
+    comment_pattern2 = r"\/\**\*\/"
+
+    macro = macro.strip()
+    macro = re.sub(comment_pattern1, '', macro)
+    macro = re.sub(comment_pattern2, '', macro)
+
+    return macro
+
+def file_check_macro(file_path, report):
+    # number of conditional compiling
+    cond_compile = 0
+    # only check .c and .h file
+    if not file_path.endswith(".c") and not file_path.endswith(".h"):
+        return
+
+    with open(file_path, "r") as f:
+        while True:
+            line = f.readline()
+            if not line:
+                break
+            line = line.strip()
+            if line.startswith(cond_compile_mark):
+                cond_compile += 1
+                continue
+            if line.startswith(cond_compile_end):
+                cond_compile -= 1
+                continue
+
+            macro = re.match(macro_pattern, line)
+            if macro:
+                macro = macro_strip(macro.string)
+                while macro[-1] == '\\':
+                    macro = macro[0:-1]
+                    macro = macro.strip()
+                    macro += f.readline()
+                    macro = macro_strip(macro)
+                if not args.verbose:
+                    if file_path.endswith(".c")  and cond_compile != 0:
+                        continue
+                    # 1 is for #ifdef xxx at the beginning of the header file
+                    if file_path.endswith(".h") and cond_compile != 1:
+                        continue
+                check_macro(macro, report)
+
+def get_correct_macros(path):
+    file_check_macro(path, False)
+
+def dir_check_macro(dir_path):
+
+    for dentry in os.listdir(dir_path):
+        path = os.path.join(dir_path, dentry)
+        if os.path.isdir(path):
+            dir_check_macro(path)
+        elif os.path.isfile(path):
+            get_correct_macros(path)
+            file_check_macro(path, True)
+
+
+def main():
+    if os.path.isfile(args.path):
+        get_correct_macros(args.path)
+        file_check_macro(args.path, True)
+    elif os.path.isdir(args.path):
+        dir_check_macro(args.path)
+    else:
+        print(f"{args.path} doesn't exit or is neither a file nor a dir")
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file