[clang-tidy] Add a close-on-exec check on inotify_init1() in Android module.

[yawanng]

Summary

inotify_init1() is better to set IN_CLOEXEC flag to avoid file descriptor leakage.

[Eugene.Zelenko]

docs/ReleaseNotes.rst

60

Please sort checks in alphabetical order.

[alexfh]

See the comment on D35372.

[hokein]

clang-tidy/android/CloexecInotifyInit1Check.cpp

29

nit: /*MarcoFlag=*/

test/clang-tidy/android-cloexec-inotify-init1.cpp

20

The same, trailing ;.

[hokein]

LGTM

clang-tidy/android/AndroidTidyModule.cpp

 #include "../ClangTidyModuleRegistry.h"
 #include "CloexecCreatCheck.h"
 #include "CloexecFopenCheck.h"
+#include "CloexecInotifyInit1Check.h"
 #include "CloexecMemfdCreateCheck.h"
 #include "CloexecOpenCheck.h"
 #include "CloexecSocketCheck.h"

   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     CheckFactories.registerCheck<CloexecCreatCheck>("android-cloexec-creat");
     CheckFactories.registerCheck<CloexecFopenCheck>("android-cloexec-fopen");
+    CheckFactories.registerCheck<CloexecInotifyInit1Check>(
+        "android-cloexec-inotify-init1");
     CheckFactories.registerCheck<CloexecMemfdCreateCheck>(
         "android-cloexec-memfd-create");
     CheckFactories.registerCheck<CloexecOpenCheck>("android-cloexec-open");

clang-tidy/android/CMakeLists.txt

   CloexecCheck.cpp
   CloexecCreatCheck.cpp
   CloexecFopenCheck.cpp
+  CloexecInotifyInit1Check.cpp
   CloexecMemfdCreateCheck.cpp
   CloexecOpenCheck.cpp
   CloexecSocketCheck.cpp

clang-tidy/android/CloexecInotifyInit1Check.h

+//===--- CloexecInotifyInit1Check.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_INOTIFY_INIT1_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_INOTIFY_INIT1_H
+
+#include "CloexecCheck.h"
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+/// Finds code that uses inotify_init1() without using the IN_CLOEXEC flag.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-inotify-init1.html
+class CloexecInotifyInit1Check : public CloexecCheck {
+public:
+  CloexecInotifyInit1Check(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_INOTIFY_INIT1_H

clang-tidy/android/CloexecInotifyInit1Check.cpp

+//===--- CloexecInotifyInit1Check.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 "CloexecInotifyInit1Check.h"
+#include "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+void CloexecInotifyInit1Check::registerMatchers(MatchFinder *Finder) {
+  registerMatchersImpl(
+      Finder, functionDecl(returns(isInteger()), hasName("inotify_init1"),
+                           hasParameter(0, hasType(isInteger()))));
+}
+
+void CloexecInotifyInit1Check::check(const MatchFinder::MatchResult &Result) {
+  insertMacroFlag(Result, /*MarcoFlag=*/"IN_CLOEXEC", /*ArgPos=*/0);
+}
+
+} // namespace android
+} // namespace tidy
+} // namespace clang

docs/ReleaseNotes.rst

   Finds cases where integer division in a floating point context is likely to
   cause unintended loss of precision.
 
+- New `android-cloexec-inotify-init1
+  <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-inotify-init1.html>`_ check
+
+  Checks if the required file flag ``IN_CLOEXEC`` is present in the argument of
+  ``inotify_init1()``.
+
 - New `readability-static-accessed-through-instance
   <http://clang.llvm.org/extra/clang-tidy/checks/readability-static-accessed-through-instance.html>`_ check
 

docs/clang-tidy/checks/android-cloexec-inotify-init1.rst

+.. title:: clang-tidy - android-cloexec-inotify-init1
+
+android-cloexec-inotify-init1
+=============================
+
+``inotify_init1()`` should include ``IN_CLOEXEC`` in its type argument to avoid the
+file descriptor leakage. Without this flag, an opened sensitive file would
+remain open across a fork+exec to a lower-privileged SELinux domain.
+
+Examples:
+
+.. code-block:: c++
+
+  inotify_init1(IN_NONBLOCK);
+
+  // becomes
+
+  inotify_init1(IN_NONBLOCK | IN_CLOEXEC);

docs/clang-tidy/checks/list.rst

 .. toctree::
    android-cloexec-creat
    android-cloexec-fopen
+   android-cloexec-inotify-init1
    android-cloexec-memfd-create
    android-cloexec-open
    android-cloexec-socket

test/clang-tidy/android-cloexec-inotify-init1.cpp

+// RUN: %check_clang_tidy %s android-cloexec-inotify-init1 %t
+
+#define IN_NONBLOCK 1
+#define __O_CLOEXEC 3
+#define IN_CLOEXEC __O_CLOEXEC
+#define TEMP_FAILURE_RETRY(exp) \
+  ({                            \
+    int _rc;                    \
+    do {                        \
+      _rc = (exp);              \
+    } while (_rc == -1);        \
+  })
+
+extern "C" int inotify_init1(int flags);
+
+void a() {
+  inotify_init1(IN_NONBLOCK);
+  // CHECK-MESSAGES: :[[@LINE-1]]:28: warning: 'inotify_init1' should use IN_CLOEXEC where possible [android-cloexec-inotify-init1]
+  // CHECK-FIXES: inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+  TEMP_FAILURE_RETRY(inotify_init1(IN_NONBLOCK));
+  // CHECK-MESSAGES: :[[@LINE-1]]:47: warning: 'inotify_init1'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(inotify_init1(IN_NONBLOCK | IN_CLOEXEC));
+}
+
+void f() {
+  inotify_init1(0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: 'inotify_init1'
+  // CHECK-FIXES: inotify_init1(IN_CLOEXEC);
+  TEMP_FAILURE_RETRY(inotify_init1(0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: 'inotify_init1'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(inotify_init1(IN_CLOEXEC));
+
+  int flag = 1;
+  inotify_init1(flag);
+  TEMP_FAILURE_RETRY(inotify_init1(flag));
+}
+
+namespace i {
+int inotify_init1(int flags);
+
+void d() {
+  inotify_init1(IN_NONBLOCK);
+  TEMP_FAILURE_RETRY(inotify_init1(IN_NONBLOCK));
+}
+
+} // namespace i
+
+void e() {
+  inotify_init1(IN_CLOEXEC);
+  TEMP_FAILURE_RETRY(inotify_init1(IN_CLOEXEC));
+  inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+  TEMP_FAILURE_RETRY(inotify_init1(IN_NONBLOCK | IN_CLOEXEC));
+}
+
+class G {
+public:
+  int inotify_init1(int flags);
+  void d() {
+    inotify_init1(IN_CLOEXEC);
+    TEMP_FAILURE_RETRY(inotify_init1(IN_CLOEXEC));
+    inotify_init1(IN_NONBLOCK | IN_CLOEXEC);
+    TEMP_FAILURE_RETRY(inotify_init1(IN_NONBLOCK | IN_CLOEXEC));
+  }
+};