Don't allow child process to clobber environ

src/node_child_process.cc

@@ -302,6 +302,10 @@ int ChildProcess::Spawn(const char *file, char *const args[], char **env) {
     return -3;
   }
 
+  // Save environ in the case that we get it clobbered
+  // by the child process.
+  char **save_our_env = environ;
+
   switch (pid_ = vfork()) {
     case -1:  // Error.
       Shutdown();
@@ -324,6 +328,9 @@ int ChildProcess::Spawn(const char *file, char *const args[], char **env) {
       _exit(127);
   }
 
+  // Restore environment.
+  environ = save_our_env;
+
   // Parent.
 
   ev_child_set(&child_watcher_, pid_, 0);