[clang-tidy] Add a close-on-exec check on accept() in Android module.

[chh]

Summary

accept() is better to be replaced by accept4() with SOCK_CLOEXEC flag to avoid file descriptor leakage.

[alexfh]

See the comment on D35372.

[alexfh]

LG with a nit.

clang-tidy/android/CloexecAcceptCheck.cpp

42 ↗

(On Diff #110758)

Two minor issues here:

1. FixMsg name is misleading, specifically the "Msg" part, since it's not a message.
2. there's no need to use an argument comment, where it's clear what the actual argument's meaning is. E.g. ReplacementText is pretty clear on its own. As is the warning message above.

[chh]

clang-tidy/android/CloexecAcceptCheck.cpp

42 ↗

(On Diff #110758)

Done.

clang-tools-extra/trunk/clang-tidy/android/AndroidTidyModule.cpp

 //===--- AndroidTidyModule.cpp - clang-tidy--------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
+#include "CloexecAcceptCheck.h"
 #include "CloexecCreatCheck.h"
 #include "CloexecDupCheck.h"
 #include "CloexecFopenCheck.h"
 #include "CloexecInotifyInit1Check.h"
 #include "CloexecInotifyInitCheck.h"
 #include "CloexecMemfdCreateCheck.h"
 #include "CloexecOpenCheck.h"
 #include "CloexecSocketCheck.h"
 
 using namespace clang::ast_matchers;
 
 namespace clang {
 namespace tidy {
 namespace android {
 
 /// This module is for Android specific checks.
 class AndroidModule : public ClangTidyModule {
 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
+    CheckFactories.registerCheck<CloexecAcceptCheck>("android-cloexec-accept");
     CheckFactories.registerCheck<CloexecCreatCheck>("android-cloexec-creat");
     CheckFactories.registerCheck<CloexecDupCheck>("android-cloexec-dup");
     CheckFactories.registerCheck<CloexecFopenCheck>("android-cloexec-fopen");
     CheckFactories.registerCheck<CloexecInotifyInitCheck>(
         "android-cloexec-inotify-init");
     CheckFactories.registerCheck<CloexecInotifyInit1Check>(
         "android-cloexec-inotify-init1");
     CheckFactories.registerCheck<CloexecMemfdCreateCheck>(

clang-tools-extra/trunk/clang-tidy/android/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS support)
 
 add_clang_library(clangTidyAndroidModule
   AndroidTidyModule.cpp
+  CloexecAcceptCheck.cpp
   CloexecCheck.cpp
   CloexecCreatCheck.cpp
   CloexecDupCheck.cpp
   CloexecFopenCheck.cpp
   CloexecInotifyInit1Check.cpp
   CloexecInotifyInitCheck.cpp
   CloexecMemfdCreateCheck.cpp
   CloexecOpenCheck.cpp

clang-tools-extra/trunk/clang-tidy/android/CloexecAcceptCheck.h

+//===--- CloexecAcceptCheck.h - clang-tidy-----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_ACCEPT_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_ACCEPT_H
+
+#include "CloexecCheck.h"
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+/// accept() is better to be replaced by accept4().
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-accept.html
+class CloexecAcceptCheck : public CloexecCheck {
+public:
+  CloexecAcceptCheck(StringRef Name, ClangTidyContext *Context)
+      : CloexecCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace android
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_ACCEPT_H

clang-tools-extra/trunk/clang-tidy/android/CloexecAcceptCheck.cpp

+//===--- CloexecAcceptCheck.cpp - clang-tidy-------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "CloexecAcceptCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+void CloexecAcceptCheck::registerMatchers(MatchFinder *Finder) {
+  auto SockAddrPointerType =
+      hasType(pointsTo(recordDecl(isStruct(), hasName("sockaddr"))));
+  auto SockLenPointerType = hasType(pointsTo(namedDecl(hasName("socklen_t"))));
+
+  registerMatchersImpl(Finder,
+                       functionDecl(returns(isInteger()), hasName("accept"),
+                                    hasParameter(0, hasType(isInteger())),
+                                    hasParameter(1, SockAddrPointerType),
+                                    hasParameter(2, SockLenPointerType)));
+}
+
+void CloexecAcceptCheck::check(const MatchFinder::MatchResult &Result) {
+  const std::string &ReplacementText =
+      (Twine("accept4(") + getSpellingArg(Result, 0) + ", " +
+       getSpellingArg(Result, 1) + ", " + getSpellingArg(Result, 2) +
+       ", SOCK_CLOEXEC)")
+          .str();
+
+  replaceFunc(
+      Result,
+      "prefer accept4() to accept() because accept4() allows SOCK_CLOEXEC",
+      ReplacementText);
+}
+
+} // namespace android
+} // namespace tidy
+} // namespace clang

clang-tools-extra/trunk/docs/ReleaseNotes.rst

* **performance-implicit-cast-in-loop** was renamed to
       <http://clang.llvm.org/extra/clang-tidy/checks/performance-implicit-conversion-in-loop.html>`_
     * **readability-implicit-bool-cast** was renamed to
       `readability-implicit-bool-conversion
       <http://clang.llvm.org/extra/clang-tidy/checks/readability-implicit-bool-conversion.html>`_;
       the check's options were renamed as follows:
       ``AllowConditionalIntegerCasts`` -> ``AllowIntegerConditions``,
       ``AllowConditionalPointerCasts`` -> ``AllowPointerConditions``.
 
+- New `android-cloexec-accept
+  <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-accept.html>`_ check
+
+  Detects usage of ``accept()``.
+
 - New `android-cloexec-dup
   <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-dup.html>`_ check
 
   Detects usage of ``dup()``.
 
 - New `android-cloexec-inotify-init
   <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-inotify-init.html>`_ check
 

clang-tools-extra/trunk/docs/clang-tidy/checks/android-cloexec-accept.rst

+.. title:: clang-tidy - android-cloexec-accept
+
+android-cloexec-accept
+======================
+
+The usage of ``accept()`` is not recommended, it's better to use ``accept4()``.
+Without this flag, an opened sensitive file descriptor would remain open across
+a fork+exec to a lower-privileged SELinux domain.
+
+Examples:
+
+.. code-block:: c++
+
+  accept(sockfd, addr, addrlen);
+
+  // becomes
+
+  accept4(sockfd, addr, addrlen, SOCK_CLOEXEC);

clang-tools-extra/trunk/docs/clang-tidy/checks/list.rst

 .. title:: clang-tidy - Clang-Tidy Checks
 
 Clang-Tidy Checks
 =================
 
 .. toctree::
+   android-cloexec-accept
    android-cloexec-creat
    android-cloexec-dup
    android-cloexec-fopen
    android-cloexec-inotify-init
    android-cloexec-inotify-init1
    android-cloexec-memfd-create
    android-cloexec-open
    android-cloexec-socket

clang-tools-extra/trunk/test/clang-tidy/android-cloexec-accept.cpp

+// RUN: %check_clang_tidy %s android-cloexec-accept %t
+
+struct sockaddr {};
+typedef int socklen_t;
+#define NULL 0
+
+extern "C" int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
+
+void f() {
+  accept(0, NULL, NULL);
+  // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: prefer accept4() to accept() because accept4() allows SOCK_CLOEXEC [android-cloexec-accept]
+  // CHECK-FIXES: accept4(0, NULL, NULL, SOCK_CLOEXEC);
+}
+
+namespace i {
+int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
+void g() {
+  accept(0, NULL, NULL);
+}
+} // namespace i
+
+class C {
+public:
+  int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
+  void h() {
+    accept(0, NULL, NULL);
+  }
+};