Thread safe initialization of OSCrypt cache

components/os_crypt/os_crypt_linux.cc

Index: components/os_crypt/os_crypt_linux.cc
diff --git a/components/os_crypt/os_crypt_linux.cc b/components/os_crypt/os_crypt_linux.cc
index 68ea402dd9a3ea1c6a2bdb9212f2cb5d17d18a92..86503382b4f43466b918746aabb6097aee847413 100644
--- a/components/os_crypt/os_crypt_linux.cc
+++ b/components/os_crypt/os_crypt_linux.cc
@@ -14,6 +14,7 @@
 #include "base/logging.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/synchronization/lock.h"
 #include "components/os_crypt/key_storage_linux.h"
 #include "crypto/encryptor.h"
 #include "crypto/symmetric_key.h"
@@ -54,6 +55,9 @@ struct Cache {
   std::unique_ptr<std::string> password_v11_cache;
   bool is_key_storage_cached;
   bool is_password_v11_cached;
+  // Guards access to |g_cache|, making lazy initialization of individual parts
+  // thread safe.
+  base::Lock lock;
 };
 
 base::LazyInstance<Cache>::Leaky g_cache = LAZY_INSTANCE_INITIALIZER;
@@ -68,20 +72,23 @@ KeyStorageLinux* GetKeyStorage() {
   return g_cache.Get().key_storage_cache.get();
 }
 
-// Returns a cached string of "peanuts".
+// Returns a cached string of "peanuts". Is thread-safe.
 std::string* GetPasswordV10() {
-  if (!g_cache.Get().password_v10_cache.get())
+  base::AutoLock auto_lock(g_cache.Get().lock);
+  if (!g_cache.Get().password_v10_cache.get()) {
     g_cache.Get().password_v10_cache.reset(new std::string("peanuts"));
+  }
   return g_cache.Get().password_v10_cache.get();
 }
 
 // Caches and returns the password from the KeyStorage or null if there is no
-// service.
+// service. Is thread-safe.
 std::string* GetPasswordV11() {
+  base::AutoLock auto_lock(g_cache.Get().lock);
   if (!g_cache.Get().is_password_v11_cached) {
-    g_cache.Get().is_password_v11_cached = true;
     g_cache.Get().password_v11_cache.reset(
         GetKeyStorage() ? new std::string(GetKeyStorage()->GetKey()) : nullptr);
+    g_cache.Get().is_password_v11_cached = true;
   }
   return g_cache.Get().password_v11_cache.get();
 }
@@ -248,13 +255,16 @@ void UseMockKeyStorageForTesting(KeyStorageLinux* (*get_key_storage_mock)(),
 
   if (get_key_storage_mock && get_password_v11_mock) {
     // Bypass calling KeyStorage::CreateService and caching of the key for V11
-    g_get_password[Version::V11] = get_password_v11_mock;
+    if (get_password_v11_mock)
+      g_get_password[Version::V11] = get_password_v11_mock;
     // OSCrypt will determine the encryption version by checking if a
     // |KeyStorage| instance can be created. Enable V11 by returning the mock.
-    g_key_storage_provider = get_key_storage_mock;
+    if (get_key_storage_mock)
+      g_key_storage_provider = get_key_storage_mock;
   } else {
     // Restore real implementation
     std::copy(std::begin(get_password_save), std::end(get_password_save),
               std::begin(g_get_password));
+    g_key_storage_provider = &GetKeyStorage;
   }
 }