src: don't overwrite non-writable vm globals

Check that the property doesn't have the read-only flag set before
overwriting it.

This is Ben Noordhuis previous commit, but keeping
is_contextual_store. is_contextual_store describes whether
this.foo = 42 or foo = 42 was called. The second is contextual
and will fail in strict mode if foo is used without
declaration. Therefore only do an early return if it is
a contextual store. In particular, don't do an early
return for Object.defineProperty(this, ...).

Fixes: https://github.com/nodejs/node/issues/10223
Refs: https://github.com/nodejs/node/pull/10227
PR-URL: https://github.com/nodejs/node/pull/11109
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/test/parallel/test-vm-context.js b/test/parallel/test-vm-context.js
index 75d91ce812..c58bdc29da 100644
--- a/test/parallel/test-vm-context.js
+++ b/test/parallel/test-vm-context.js
@@ -75,3 +75,16 @@ assert.throws(function() {
 // https://github.com/nodejs/node/issues/6158
 ctx = new Proxy({}, {});
 assert.strictEqual(typeof vm.runInNewContext('String', ctx), 'function');
+
+// https://github.com/nodejs/node/issues/10223
+ctx = vm.createContext();
+vm.runInContext('Object.defineProperty(this, "x", { value: 42 })', ctx);
+assert.strictEqual(ctx.x, 42);
+assert.strictEqual(vm.runInContext('x', ctx), 42);
+
+vm.runInContext('x = 0', ctx);                      // Does not throw but x...
+assert.strictEqual(vm.runInContext('x', ctx), 42);  // ...should be unaltered.
+
+assert.throws(() => vm.runInContext('"use strict"; x = 0', ctx),
+              /Cannot assign to read only property 'x'/);
+assert.strictEqual(vm.runInContext('x', ctx), 42);