http2: stop reading from socket if writes are in progress

If a write to the underlying socket finishes asynchronously, that means that we cannot write any more data at that point without waiting for it to finish. If this happens, we should also not be producing any more input. This is part of mitigating CVE-2019-9511/CVE-2019-9517. PR-URL: #29122 Reviewed-By: Rich Trott <[email protected]> Reviewed-By: James M Snell <[email protected]>
nodejs · Aug 15, 2019 · f64515b · f64515b
1 parent ba332df
commit f64515b
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Showing 2 changed files with 18 additions and 1 deletion.
diff --git a/src/node_http2.cc b/src/node_http2.cc
@@ -1542,9 +1542,18 @@ void Http2Session::HandleSettingsFrame(const nghttp2_frame* frame) {
 void Http2Session::OnStreamAfterWrite(WriteWrap* w, int status) {
   Debug(this, "write finished with status %d", status);
 
+  CHECK_NE(flags_ & SESSION_STATE_WRITE_IN_PROGRESS, 0);
+  flags_ &= ~SESSION_STATE_WRITE_IN_PROGRESS;
+
   // Inform all pending writes about their completion.
   ClearOutgoing(status);
 
+  if ((flags_ & SESSION_STATE_READING_STOPPED) &&
+      nghttp2_session_want_read(session_)) {
+    flags_ &= ~SESSION_STATE_READING_STOPPED;
+    stream_->ReadStart();
+  }
+
   if (!(flags_ & SESSION_STATE_WRITE_SCHEDULED)) {
     // Schedule a new write if nghttp2 wants to send data.
     MaybeScheduleWrite();
@@ -1582,10 +1591,13 @@ void Http2Session::MaybeScheduleWrite() {
 }
 
 void Http2Session::MaybeStopReading() {
+  if (flags_ & SESSION_STATE_READING_STOPPED) return;
   int want_read = nghttp2_session_want_read(session_);
   Debug(this, "wants read? %d", want_read);
-  if (want_read == 0)
+  if (want_read == 0 || (flags_ & SESSION_STATE_WRITE_IN_PROGRESS)) {
+    flags_ |= SESSION_STATE_READING_STOPPED;
     stream_->ReadStop();
+  }
 }
 
 // Unset the sending state, finish up all current writes, and reset
@@ -1716,8 +1728,11 @@ uint8_t Http2Session::SendPendingData() {
 
   chunks_sent_since_last_write_++;
 
+  CHECK_EQ(flags_ & SESSION_STATE_WRITE_IN_PROGRESS, 0);
+  flags_ |= SESSION_STATE_WRITE_IN_PROGRESS;
   StreamWriteResult res = underlying_stream()->Write(*bufs, count);
   if (!res.async) {
+    flags_ &= ~SESSION_STATE_WRITE_IN_PROGRESS;
     ClearOutgoing(res.err);
   }
 

diff --git a/src/node_http2.h b/src/node_http2.h
@@ -335,6 +335,8 @@ enum session_state_flags {
   SESSION_STATE_CLOSED = 0x4,
   SESSION_STATE_CLOSING = 0x8,
   SESSION_STATE_SENDING = 0x10,
+  SESSION_STATE_WRITE_IN_PROGRESS = 0x20,
+  SESSION_STATE_READING_STOPPED = 0x40,
 };
 
 typedef uint32_t(*get_setting)(nghttp2_session* session,