From ca39214f4e9fddf247e880ef9562865be850fce6 Mon Sep 17 00:00:00 2001
From: Ben Langmuir <blangmuir@apple.com>
Date: Mon, 19 May 2014 16:13:45 +0000
Subject: [PATCH] Fix use-after-free and spurious error during module load

FileManager::invalidateCache is not safe to call when there may be
existing references to the file. What module load failure needs is
to refresh so stale stat() info isn't stored.

This may be the last user of invalidateCache; I'll take a look and
remove it if possible in a future commit.

This caused a use-after-free error as well as a spurious error message
that a module was "found in both 'X.pcm' and 'X.pcm'" in some cases.

llvm-svn: 209138
---
 clang/lib/Serialization/ModuleManager.cpp | 15 ++++++++++++--
 clang/test/Modules/load-after-failure.m   | 25 +++++++++++++++++++++++
 2 files changed, 38 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/Modules/load-after-failure.m

diff --git a/clang/lib/Serialization/ModuleManager.cpp b/clang/lib/Serialization/ModuleManager.cpp
index 66f18158a69d..c3152c0b0216 100644
--- a/clang/lib/Serialization/ModuleManager.cpp
+++ b/clang/lib/Serialization/ModuleManager.cpp
@@ -152,9 +152,20 @@ void ModuleManager::removeModules(ModuleIterator first, ModuleIterator last,
 
   // Delete the modules and erase them from the various structures.
   for (ModuleIterator victim = first; victim != last; ++victim) {
-    Modules.erase((*victim)->File);
+    const FileEntry *F = (*victim)->File;
+    Modules.erase(F);
+
+    // Refresh the stat() information for the module file so stale information
+    // doesn't get stored accidentally.
+    vfs::Status UpdatedStat;
+    if (FileMgr.getNoncachedStatValue(F->getName(), UpdatedStat)) {
+      llvm::report_fatal_error(Twine("module file '") + F->getName() +
+                               "' removed after it has been used");
+    } else {
+      FileMgr.modifyFileEntry(const_cast<FileEntry *>(F), UpdatedStat.getSize(),
+          UpdatedStat.getLastModificationTime().toEpochTime());
+    }
 
-    FileMgr.invalidateCache((*victim)->File);
     if (modMap) {
       StringRef ModuleName = (*victim)->ModuleName;
       if (Module *mod = modMap->findModule(ModuleName)) {
diff --git a/clang/test/Modules/load-after-failure.m b/clang/test/Modules/load-after-failure.m
new file mode 100644
index 000000000000..f471fd88d505
--- /dev/null
+++ b/clang/test/Modules/load-after-failure.m
@@ -0,0 +1,25 @@
+// REQUIRES: shell
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+
+// RUN: echo '@import B;' > %t/A.h
+// RUN: echo '@import C;' > %t/B.h
+// RUN: echo '@import D;' >> %t/B.h
+// RUN: echo '// C.h' > %t/C.h
+// RUN: echo '// D.h' > %t/D.h
+// RUN: echo 'module A { header "A.h" }' > %t/module.modulemap
+// RUN: echo 'module B { header "B.h" }' >> %t/module.modulemap
+// RUN: echo 'module C { header "C.h" }' >> %t/module.modulemap
+// RUN: echo 'module D { header "D.h" }' >> %t/module.modulemap
+
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %t %s -verify
+// RUN: echo " " >> %t/D.h
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %t %s -verify
+// expected-no-diagnostics
+
+
+@import C;
+@import A;
+@import C;
+// When compiling A, C will be be loaded then removed when D fails. Ensure
+// this does not cause problems importing C again later.