buffer: zero-fill buffer allocated with invalid content

Zero-fill when `Buffer.alloc()` receives invalid fill data.

A solution like https://github.com/nodejs/node/pull/17427 which switches
to throwing makes sense, but is likely a breaking change.

This suggestion leaves the behaviour of `buffer.fill()` untouched,
since any change to it would be a breaking change, and lets
`Buffer.alloc()` check whether any filling took place or not.

PR-URL: https://github.com/nodejs/node/pull/17428
Refs: https://github.com/nodejs/node/pull/17427
Refs: https://github.com/nodejs/node/issues/17423
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/src/node_buffer.cc b/src/node_buffer.cc
index e810760790..ca2c6a89cb 100644
--- a/src/node_buffer.cc
+++ b/src/node_buffer.cc
@@ -591,6 +591,8 @@ void Fill(const FunctionCallbackInfo<Value>& args) {
   THROW_AND_RETURN_IF_OOB(start <= end);
   THROW_AND_RETURN_IF_OOB(fill_length + start <= ts_obj_length);
 
+  args.GetReturnValue().Set(static_cast<double>(fill_length));
+
   // First check if Buffer has been passed.
   if (Buffer::HasInstance(args[1])) {
     SPREAD_BUFFER_ARG(args[1], fill_obj);
@@ -612,8 +614,10 @@ void Fill(const FunctionCallbackInfo<Value>& args) {
       enc == UTF8 ? str_obj->Utf8Length() :
       enc == UCS2 ? str_obj->Length() * sizeof(uint16_t) : str_obj->Length();
 
-  if (str_length == 0)
+  if (str_length == 0) {
+    args.GetReturnValue().Set(0);
     return;
+  }
 
   // Can't use StringBytes::Write() in all cases. For example if attempting
   // to write a two byte character into a one byte Buffer.
@@ -643,7 +647,7 @@ void Fill(const FunctionCallbackInfo<Value>& args) {
     // TODO(trevnorris): Should this throw? Because of the string length was
     // greater than 0 but couldn't be written then the string was invalid.
     if (str_length == 0)
-      return;
+      return args.GetReturnValue().Set(0);
   }
 
  start_fill: