src: CHECK() for argument overflow in Spawn()

This commit adds checks for overflow to args and env in Spawn().
It seems extremely unlikely that either of these values would
overflow from a valid use case.

Fixes: nodejs#15622
PR-URL: nodejs#16761
Reviewed-By: Gireesh Punathil <[email protected]>

Author: cjihrig

src/process_wrap.cc

@@ -185,6 +185,8 @@ class ProcessWrap : public HandleWrap {
     if (!argv_v.IsEmpty() && argv_v->IsArray()) {
       Local<Array> js_argv = Local<Array>::Cast(argv_v);
       int argc = js_argv->Length();
+      CHECK_GT(argc + 1, 0);  // Check for overflow.
+
       // Heap allocate to detect errors. +1 is for nullptr.
       options.args = new char*[argc + 1];
       for (int i = 0; i < argc; i++) {
@@ -211,6 +213,7 @@ class ProcessWrap : public HandleWrap {
     if (!env_v.IsEmpty() && env_v->IsArray()) {
       Local<Array> env_opt = Local<Array>::Cast(env_v);
       int envc = env_opt->Length();
+      CHECK_GT(envc + 1, 0);  // Check for overflow.
       options.env = new char*[envc + 1];  // Heap allocated to detect errors.
       for (int i = 0; i < envc; i++) {
         node::Utf8Value pair(env->isolate(),