[#1590] node: Smart memory allocation in GetRange

Allocate memory only if a node chosen as the forwarded request receiver
has responded with a successful status.

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

CHANGELOG.md

@@ -14,6 +14,7 @@ Changelog for NeoFS Node
 - Do not replicate object twice to the same node (#1410)
 - Concurrent object handling by the Policer (#1411)
 - Attaching API version to the forwarded requests (#1581)
+- Node OOM panics on `GetRange` request with extremely huge range length (#1590)
 
 ### Removed
 

pkg/services/object/get/v2/util.go

@@ -250,7 +250,8 @@ func (s *Service) toRangePrm(req *objectV2.GetRangeRequest, stream objectSvc.Get
 				return nil, fmt.Errorf("could not create Get payload range stream: %w", err)
 			}
 
-			payload := make([]byte, 0, body.GetRange().GetLength())
+			// allocate memory only after receiving a successful response
+			var payload []byte
 
 			resp := new(objectV2.GetRangeResponse)
 
@@ -283,6 +284,10 @@ func (s *Service) toRangePrm(req *objectV2.GetRangeRequest, stream objectSvc.Get
 				case nil:
 					return nil, fmt.Errorf("unexpected range type %T", v)
 				case *objectV2.GetRangePartChunk:
+					if payload == nil {
+						payload = make([]byte, 0, body.GetRange().GetLength())
+					}
+
 					payload = append(payload, v.GetChunk()...)
 				case *objectV2.SplitInfo:
 					si := object.NewSplitInfoFromV2(v)