[clang-tidy] Add a close-on-exec check on epoll_create1() in Android module.

[yawanng]

Summary

epoll_create1() is better to set EPOLL_CLOEXEC flag to avoid file descriptor leakage.

[Eugene.Zelenko]

clang-tidy/android/CloexecEpollCreate1Check.cpp

22

Please make this declaration consent across all checks. In some checks it declared inside namespaces, in some - outside.

docs/ReleaseNotes.rst

60

Please sort checks in alphabetical order.

[alexfh]

See the comment on D35372.

[alexfh]

LG

clang-tidy/android/AndroidTidyModule.cpp

 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
 #include "CloexecCreatCheck.h"
+#include "CloexecEpollCreate1Check.h"
 #include "CloexecFopenCheck.h"
 #include "CloexecOpenCheck.h"
 #include "CloexecSocketCheck.h"

 public:
   void addCheckFactories(ClangTidyCheckFactories &CheckFactories) override {
     CheckFactories.registerCheck<CloexecCreatCheck>("android-cloexec-creat");
+    CheckFactories.registerCheck<CloexecEpollCreate1Check>(
+        "android-cloexec-epoll-create1");
     CheckFactories.registerCheck<CloexecFopenCheck>("android-cloexec-fopen");
     CheckFactories.registerCheck<CloexecOpenCheck>("android-cloexec-open");
     CheckFactories.registerCheck<CloexecSocketCheck>("android-cloexec-socket");

clang-tidy/android/CMakeLists.txt

 add_clang_library(clangTidyAndroidModule
   AndroidTidyModule.cpp
   CloexecCreatCheck.cpp
+  CloexecEpollCreate1Check.cpp
   CloexecFopenCheck.cpp
   CloexecOpenCheck.cpp
   CloexecSocketCheck.cpp

clang-tidy/android/CloexecEpollCreate1Check.h

+//===--- CloexecEpollCreate1Check.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_EPOLL_CREATE1_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_ANDROID_CLOEXEC_EPOLL_CREATE1_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace android {
+
+/// Finds code that uses epoll_create1() without using the EPOLL_CLOEXEC flag.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-epoll-create1.html
+class CloexecEpollCreate1Check : public ClangTidyCheck {
+public:
+  CloexecEpollCreate1Check(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(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_EPOLL_CREATE1_H

clang-tidy/android/CloexecEpollCreate1Check.cpp

+//===--- CloexecEpollCreate1Check.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 "CloexecEpollCreate1Check.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 {
+
+static constexpr const char *EPOLL_CLOEXEC = "EPOLL_CLOEXEC";
+
+void CloexecEpollCreate1Check::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      callExpr(callee(functionDecl(isExternC(), returns(isInteger()),
+                                   hasName("epoll_create1"),
+                                   hasParameter(0, hasType(isInteger())))
+                          .bind("funcDecl")))
+          .bind("epollCreate1Fn"),
+      this);
+}
+
+void CloexecEpollCreate1Check::check(const MatchFinder::MatchResult &Result) {
+  const auto *MatchedCall = Result.Nodes.getNodeAs<CallExpr>("epollCreate1Fn");
+  const auto *FD = Result.Nodes.getNodeAs<FunctionDecl>("funcDecl");
+  const Expr *FlagArg = MatchedCall->getArg(0);
+  SourceManager &SM = *Result.SourceManager;
+
+  if (utils::exprHasBitFlagWithSpelling(FlagArg->IgnoreParenCasts(), SM,
+                                        Result.Context->getLangOpts(),
+                                        EPOLL_CLOEXEC))
+    return;
+
+  SourceLocation EndLoc =
+      Lexer::getLocForEndOfToken(SM.getFileLoc(FlagArg->getLocEnd()), 0, SM,
+                                 Result.Context->getLangOpts());
+
+  diag(EndLoc, "%0 should use %1 where possible")
+      << FD << EPOLL_CLOEXEC
+      << FixItHint::CreateInsertion(EndLoc,
+                                    (Twine(" | ") + EPOLL_CLOEXEC).str());
+}
+
+} // namespace android
+} // namespace tidy
+} // namespace clang

docs/ReleaseNotes.rst

 
   Detect usage of ``creat()``.
 
+- New `android-cloexec-epoll-create1
+  <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-epoll-create1.html>`_ check
+
+  Checks if the required file flag ``EPOLL_CLOEXEC`` is present in the argument of
+  ``epoll_create1()``.
+
 - New `android-cloexec-open
   <http://clang.llvm.org/extra/clang-tidy/checks/android-cloexec-open.html>`_ check
 

docs/clang-tidy/checks/android-cloexec-epoll-create1.rst

+.. title:: clang-tidy - android-cloexec-epoll-create1
+
+android-cloexec-epoll-create1
+=============================
+
+``epoll_create1()`` should include ``EPOLL_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++
+
+  epoll_create1(0);
+
+  // becomes
+
+  epoll_create1(EPOLL_CLOEXEC);

docs/clang-tidy/checks/list.rst

 
 .. toctree::
    android-cloexec-creat
+   android-cloexec-epoll-create1
    android-cloexec-fopen
    android-cloexec-open
    android-cloexec-socket

test/clang-tidy/android-cloexec-epoll-create1.cpp

+// RUN: %check_clang_tidy %s android-cloexec-epoll-create1 %t
+
+#define __O_CLOEXEC 3
+#define EPOLL_CLOEXEC __O_CLOEXEC
+#define TEMP_FAILURE_RETRY(exp) \
+  ({                            \
+    int _rc;                    \
+    do {                        \
+      _rc = (exp);              \
+    } while (_rc == -1);        \
+  })
+
+extern "C" int epoll_create1(int flags);
+
+void a() {
+  epoll_create1(0);
+  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: 'epoll_create1' should use EPOLL_CLOEXEC where possible [android-cloexec-epoll-create1]
+  // CHECK-FIXES: epoll_create1(EPOLL_CLOEXEC)
+  TEMP_FAILURE_RETRY(epoll_create1(0));
+  // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: 'epoll_create1'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(epoll_create1(EPOLL_CLOEXEC))
+}
+
+void f() {
+  epoll_create1(3);
+  // CHECK-MESSAGES: :[[@LINE-1]]:18: warning: 'epoll_create1'
+  // CHECK-FIXES: epoll_create1(EPOLL_CLOEXEC)
+  TEMP_FAILURE_RETRY(epoll_create1(3));
+  // CHECK-MESSAGES: :[[@LINE-1]]:37: warning: 'epoll_create1'
+  // CHECK-FIXES: TEMP_FAILURE_RETRY(epoll_create1(EPOLL_CLOEXEC))
+
+  int flag = 0;
+  epoll_create1(EPOLL_CLOEXEC);
+  TEMP_FAILURE_RETRY(epoll_create1(EPOLL_CLOEXEC));
+}
+
+namespace i {
+int epoll_create1(int flags);
+
+void d() {
+  epoll_create1(0);
+  TEMP_FAILURE_RETRY(epoll_create1(0));
+}
+
+} // namespace i
+
+void e() {
+  epoll_create1(EPOLL_CLOEXEC);
+  TEMP_FAILURE_RETRY(epoll_create1(EPOLL_CLOEXEC));
+}
+
+class G {
+public:
+  int epoll_create1(int flags);
+  void d() {
+    epoll_create1(EPOLL_CLOEXEC);
+    TEMP_FAILURE_RETRY(epoll_create1(EPOLL_CLOEXEC));
+  }
+};