[update_engine] handle NULL returns from strdup

subprocess.cc

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "update_engine/subprocess.h"
 #include <stdlib.h>
 #include <string.h>
 #include <string>
 #include <unistd.h>
 #include <vector>
 #include "base/logging.h"
@@ skipping 22 matching lines @@
 }
 
 namespace {
 void FreeArgv(char** argv) {
   for (int i = 0; argv[i]; i++) {
     free(argv[i]);
     argv[i] = NULL;
   }
 }
 
+void FreeArgvInError(char** argv) {
+  FreeArgv(argv);
+  LOG(ERROR) << "Ran out of memory copying args.";
+}
+
 // Note: Caller responsible for free()ing the returned value!
+// Will return NULL on failure and free any allocated memory.
 char** ArgPointer() {
   const char* keys[] = {"LD_LIBRARY_PATH", "PATH"};
   char** ret = new char*[arraysize(keys) + 1];
   int pointer = 0;
   for (size_t i = 0; i < arraysize(keys); i++) {
-    ret[i] = NULL;
     if (getenv(keys[i])) {
       ret[pointer] = strdup(StringPrintf("%s=%s", keys[i],
                                          getenv(keys[i])).c_str());
-      pointer++;
+      if (!ret[pointer]) {
+        FreeArgv(ret);
+        delete [] ret;
+        return NULL;
+      }
+      ++pointer;
     }
   }
+  ret[pointer] = NULL;
   return ret;
 }
 
 class ScopedFreeArgPointer {
  public:
   ScopedFreeArgPointer(char** arr) : arr_(arr) {}
   ~ScopedFreeArgPointer() {
     if (!arr_)
       return;
     for (int i = 0; arr_[i]; i++)
       free(arr_[i]);
     delete[] arr_;
   }
  private:
   char** arr_;
   DISALLOW_COPY_AND_ASSIGN(ScopedFreeArgPointer);
 };
 }  // namespace {}
 
 uint32_t Subprocess::Exec(const std::vector<std::string>& cmd,
                           ExecCallback callback,
                           void* p) {
   GPid child_pid;
   GError* err;
   scoped_array<char*> argv(new char*[cmd.size() + 1]);
   for (unsigned int i = 0; i < cmd.size(); i++) {
     argv[i] = strdup(cmd[i].c_str());
+    if (!argv[i]) {
+      FreeArgvInError(argv.get());  // NULL in argv[i] terminates argv.
+      return 0;
+    }
   }
   argv[cmd.size()] = NULL;
 
   char** argp = ArgPointer();
+  if (!argp) {
+    FreeArgvInError(argv.get());  // NULL in argv[i] terminates argv.
+    return 0;
+  }
   ScopedFreeArgPointer argp_free(argp);
 
   SubprocessCallbackRecord callback_record;
   callback_record.callback = callback;
   callback_record.callback_data = p;
 
   bool success = g_spawn_async(NULL,  // working directory
                                argv.get(),
                                argp,
                                G_SPAWN_DO_NOT_REAP_CHILD,  // flags
@@ skipping 17 matching lines @@
     callback_records_[tag].callback = NULL;
   }
 }
 
 bool Subprocess::SynchronousExec(const std::vector<std::string>& cmd,
                                  int* return_code) {
   GError* err = NULL;
   scoped_array<char*> argv(new char*[cmd.size() + 1]);
   for (unsigned int i = 0; i < cmd.size(); i++) {
     argv[i] = strdup(cmd[i].c_str());
+    if (!argv[i]) {
+      FreeArgvInError(argv.get());  // NULL in argv[i] terminates argv.
+      return false;
+    }
   }
   argv[cmd.size()] = NULL;
 
   char** argp = ArgPointer();
+  if (!argp) {
+    FreeArgvInError(argv.get());  // NULL in argv[i] terminates argv.
+    return false;
+  }
   ScopedFreeArgPointer argp_free(argp);
 
   char* child_stdout;
 
   bool success = g_spawn_sync(NULL,  // working directory
                               argv.get(),
                               argp,
                               G_SPAWN_STDERR_TO_DEV_NULL,  // flags
                               GRedirectStderrToStdout,  // child setup function
                               NULL,  // data for child setup function
                               &child_stdout,
                               NULL,
                               return_code,
                               &err);
   FreeArgv(argv.get());
   if (err)
     LOG(INFO) << "err is: " << err->code << ", " << err->message;
   if (child_stdout && strlen(child_stdout))
     LOG(INFO) << "Subprocess output:\n" << child_stdout;
   return success;
 }
 
 Subprocess* Subprocess::subprocess_singleton_ = NULL;
 
 }  // namespace chromeos_update_engine