[ASTUnit] Fix use-after-free bug in ASTUnit::getMainBufferWithPrecompiledPreamble().

With r197755 we started reading the contents of buffer file entries, but the
buffers may point to ASTReader blobs that have been disposed.

Fix this by having the CompilerInstance object keep a reference to the ASTReader
as well as having the ASTContext keep reference to the ExternalASTSource.

This was very difficult to construct a test case for.
rdar://16149782

llvm-svn: 202346

1 files changed, 12 insertions, 7 deletions

diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 3fe8f0e82f7..cdc4b64af77 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -104,6 +104,13 @@ void CompilerInstance::setASTConsumer(ASTConsumer *Value) {
 void CompilerInstance::setCodeCompletionConsumer(CodeCompleteConsumer *Value) {
   CompletionConsumer.reset(Value);
 }
+ 
+IntrusiveRefCntPtr<ASTReader> CompilerInstance::getModuleManager() const {
+  return ModuleManager;
+}
+void CompilerInstance::setModuleManager(IntrusiveRefCntPtr<ASTReader> Reader) {
+  ModuleManager = Reader;
+}
 
 // Diagnostics
 static void SetUpDiagnosticLog(DiagnosticOptions *DiagOpts,
@@ -301,16 +308,16 @@ void CompilerInstance::createPCHExternalASTSource(StringRef Path,
                                                   bool DisablePCHValidation,
                                                 bool AllowPCHWithCompilerErrors,
                                                  void *DeserializationListener){
-  OwningPtr<ExternalASTSource> Source;
+  IntrusiveRefCntPtr<ExternalASTSource> Source;
   bool Preamble = getPreprocessorOpts().PrecompiledPreambleBytes.first != 0;
-  Source.reset(createPCHExternalASTSource(Path, getHeaderSearchOpts().Sysroot,
+  Source = createPCHExternalASTSource(Path, getHeaderSearchOpts().Sysroot,
                                           DisablePCHValidation,
                                           AllowPCHWithCompilerErrors,
                                           getPreprocessor(), getASTContext(),
                                           DeserializationListener,
                                           Preamble,
-                                       getFrontendOpts().UseGlobalModuleIndex));
-  ModuleManager = static_cast<ASTReader*>(Source.get());
+                                       getFrontendOpts().UseGlobalModuleIndex);
+  ModuleManager = static_cast<ASTReader*>(Source.getPtr());
   getASTContext().setExternalSource(Source);
 }
 
@@ -1176,9 +1183,7 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
         getASTContext().setASTMutationListener(
           getASTConsumer().GetASTMutationListener());
       }
-      OwningPtr<ExternalASTSource> Source;
-      Source.reset(ModuleManager);
-      getASTContext().setExternalSource(Source);
+      getASTContext().setExternalSource(ModuleManager);
       if (hasSema())
         ModuleManager->InitializeSema(getSema());
       if (hasASTConsumer())