From bcbd3063a3c75e9d884624cb58ed97af31ee65bc Mon Sep 17 00:00:00 2001
From: "trop[bot]" <37223003+trop[bot]@users.noreply.github.com>
Date: Fri, 13 Dec 2024 17:26:44 -0800
Subject: [PATCH] fix: custom spell-checker stuck in infinite loop (#45020)

`ReadUnicodeCharacter` updates index to the last character read, and not after it. We need to manually increment it to move to the next character.

It also doesn't validate that the index is valid, so we need to check that index is within bounds.

Refs: #44336

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Jesper Ek <deadbeef84@gmail.com>
---
 shell/renderer/api/electron_api_spell_check_client.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/shell/renderer/api/electron_api_spell_check_client.cc b/shell/renderer/api/electron_api_spell_check_client.cc
index b97f1771ff72..95e05ecccb52 100644
--- a/shell/renderer/api/electron_api_spell_check_client.cc
+++ b/shell/renderer/api/electron_api_spell_check_client.cc
@@ -32,7 +32,9 @@ namespace {
 
 bool HasWordCharacters(const std::u16string& text, size_t index) {
   base_icu::UChar32 code;
-  while (base::ReadUnicodeCharacter(text.c_str(), text.size(), &index, &code)) {
+  while (index < text.size() &&
+         base::ReadUnicodeCharacter(text.c_str(), text.size(), &index, &code)) {
+    ++index;
     UErrorCode error = U_ZERO_ERROR;
     if (uscript_getScript(code, &error) != USCRIPT_COMMON)
       return true;