Bug 1358241 - [2.1] Add mutex locking around the library handles cache. r=jchen

mozglue/linker/ElfLoader.cpp

@@ -404,12 +404,14 @@ ElfLoader::Load(const char *path, int flags, LibHandle *parent)
   /* Search the list of handles we already have for a match. When the given
    * path is not absolute, compare file names, otherwise compare full paths. */
   if (name == path) {
+    AutoLock lock(&handlesMutex);
     for (LibHandleList::iterator it = handles.begin(); it < handles.end(); ++it)
       if ((*it)->GetName() && (strcmp((*it)->GetName(), name) == 0)) {
         handle = *it;
         return handle.forget();
       }
   } else {
+    AutoLock lock(&handlesMutex);
     for (LibHandleList::iterator it = handles.begin(); it < handles.end(); ++it)
       if ((*it)->GetPath() && (strcmp((*it)->GetPath(), path) == 0)) {
         handle = *it;
@@ -458,6 +460,7 @@ ElfLoader::Load(const char *path, int flags, LibHandle *parent)
 already_AddRefed<LibHandle>
 ElfLoader::GetHandleByPtr(void *addr)
 {
+  AutoLock lock(&handlesMutex);
   /* Scan the list of handles we already have for a match */
   for (LibHandleList::iterator it = handles.begin(); it < handles.end(); ++it) {
     if ((*it)->Contains(addr)) {
@@ -508,6 +511,7 @@ ElfLoader::GetMappableFromPath(const char *path)
 void
 ElfLoader::Register(LibHandle *handle)
 {
+  AutoLock lock(&handlesMutex);
   handles.push_back(handle);
 }
 
@@ -526,6 +530,7 @@ ElfLoader::Forget(LibHandle *handle)
   /* Ensure logging is initialized or refresh if environment changed. */
   Logging::Init();
 
+  AutoLock lock(&handlesMutex);
   LibHandleList::iterator it = std::find(handles.begin(), handles.end(), handle);
   if (it != handles.end()) {
     DEBUG_LOG("ElfLoader::Forget(%p [\"%s\"])", reinterpret_cast<void *>(handle),
@@ -577,6 +582,7 @@ ElfLoader::~ElfLoader()
   libc = nullptr;
 #endif
 
+  AutoLock lock(&handlesMutex);
   /* Build up a list of all library handles with direct (external) references.
    * We actually skip system library handles because we want to keep at least
    * some of these open. Most notably, Mozilla codebase keeps a few libgnome
@@ -615,6 +621,7 @@ ElfLoader::~ElfLoader()
       }
     }
   }
+  pthread_mutex_destroy(&handlesMutex);
 }
 
 void
@@ -623,6 +630,7 @@ ElfLoader::stats(const char *when)
   if (MOZ_LIKELY(!Logging::isVerbose()))
     return;
 
+  AutoLock lock(&Singleton.handlesMutex);
   for (LibHandleList::iterator it = Singleton.handles.begin();
        it < Singleton.handles.end(); ++it)
     (*it)->stats(when);

mozglue/linker/ElfLoader.h

@@ -460,7 +460,11 @@ protected:
   const char *lastError;
 
 private:
-  ElfLoader() : expect_shutdown(true) {}
+  ElfLoader() : expect_shutdown(true)
+  {
+    pthread_mutex_init(&handlesMutex, nullptr);
+  }
+
   ~ElfLoader();
 
   /* Initialization code that can't run during static initialization. */
@@ -482,6 +486,8 @@ private:
   typedef std::vector<LibHandle *> LibHandleList;
   LibHandleList handles;
 
+  pthread_mutex_t handlesMutex;
+
 protected:
   friend class CustomElf;
   friend class LoadedElf;