From 481a0388ae7816b2b0c140014353670ebe94ea46 Mon Sep 17 00:00:00 2001
From: Allan Sandfeld Jensen <allan.jensen@qt.io>
Date: Wed, 14 Apr 2021 22:13:32 +0200
Subject: Don't parse XML symbols longer than 4096 characters

It is slow and will use too much memory.

Fixes: QTBUG-91889
Change-Id: I45c5e6038357c87bbb85b1ace17ef39a2a814ea0
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 38e111158a38507c63fd70f9ee18b9116b537976)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
---
 src/corelib/serialization/qxmlstream.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/corelib/serialization/qxmlstream.cpp b/src/corelib/serialization/qxmlstream.cpp
index 769b33931e..5f9bed99b8 100644
--- a/src/corelib/serialization/qxmlstream.cpp
+++ b/src/corelib/serialization/qxmlstream.cpp
@@ -1297,6 +1297,11 @@ inline int QXmlStreamReaderPrivate::fastScanName(int *prefix)
     int n = 0;
     uint c;
     while ((c = getChar()) != StreamEOF) {
+        if (n >= 4096) {
+            // This is too long to be a sensible name, and
+            // can exhaust memory
+            return 0;
+        }
         switch (c) {
         case '\n':
         case ' ':
-- 
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