From b263f2585ab53f56e0e22b46cf1f8519a8af8a05 Mon Sep 17 00:00:00 2001
From: Akshay K <iit.akshay@gmail.com>
Date: Mon, 26 Jul 2021 08:21:51 -0400
Subject: [PATCH] http2: on receiving rst_stream with cancel code add it to
 pending list

PR-URL: https://github.com/nodejs/node/pull/39423
Backport-PR-URL: https://github.com/nodejs/node/pull/39527
Fixes: https://github.com/nodejs/node/issues/38964
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 src/node_http2.cc | 17 +++++++++++++++++
 src/node_http2.h  | 16 ++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/node_http2.cc b/src/node_http2.cc
index dec6d7dab9ee..cc21373521e4 100644
--- a/src/node_http2.cc
+++ b/src/node_http2.cc
@@ -2135,6 +2135,23 @@ int Http2Stream::SubmitPriority(nghttp2_priority_spec* prispec,
 void Http2Stream::SubmitRstStream(const uint32_t code) {
   CHECK(!this->IsDestroyed());
   code_ = code;
+
+  // If RST_STREAM frame is received and stream is not writable
+  // because it is busy reading data, don't try force purging it.
+  // Instead add the stream to pending stream list and process
+  // the pending data when it is safe to do so. This is to avoid
+  // double free error due to unwanted behavior of nghttp2.
+  // Ref:https://github.com/nodejs/node/issues/38964
+
+  // Add stream to the pending list if it is received with scope
+  // below in the stack. The pending list may not get processed
+  // if RST_STREAM received is not in scope and added to the list
+  // causing endpoint to hang.
+  if (session_->is_in_scope() && IsReading()) {
+      session_->AddPendingRstStream(id_);
+      return;
+  }
+
   // If possible, force a purge of any currently pending data here to make sure
   // it is sent before closing the stream. If it returns non-zero then we need
   // to wait until the current write finishes and try again to avoid nghttp2
diff --git a/src/node_http2.h b/src/node_http2.h
index 045bdfd716da..a59de18f920a 100644
--- a/src/node_http2.h
+++ b/src/node_http2.h
@@ -764,6 +764,22 @@ class Http2Session : public AsyncWrap,
     return (flags_ & SESSION_STATE_CLOSED) || session_ == nullptr;
   }
 
+
+  // The changes are backported and exposes APIs to check the
+  // status flag of `Http2Session`
+#define IS_FLAG(name, flag)                                                    \
+  bool is_##name() const { return flags_ & flag; }
+
+  IS_FLAG(in_scope, SESSION_STATE_HAS_SCOPE)
+  IS_FLAG(write_scheduled, SESSION_STATE_WRITE_SCHEDULED)
+  IS_FLAG(closing, SESSION_STATE_CLOSING)
+  IS_FLAG(sending, SESSION_STATE_SENDING)
+  IS_FLAG(write_in_progress, SESSION_STATE_WRITE_IN_PROGRESS)
+  IS_FLAG(reading_stopped, SESSION_STATE_READING_STOPPED)
+  IS_FLAG(receive_paused, SESSION_STATE_NGHTTP2_RECV_PAUSED)
+
+#undef IS_FLAG
+
   // Schedule a write if nghttp2 indicates it wants to write to the socket.
   void MaybeScheduleWrite();