From 2d2f972bff73d522250bf0ebcd0708d344d37483 Mon Sep 17 00:00:00 2001
From: Vlad Zahorodnii <vlad.zahorodnii@kde.org>
Date: Wed, 31 Aug 2022 11:37:04 +0300
Subject: [PATCH] Fix loading xcursor themes with invalid Inherits field

Xcursor loading can get stuck in an infinite recursion if index.theme
file indicates that the theme inherits itself.

In order to prevent that, keep track of the loaded so far themes and
avoid loading already loaded themes.

BUG: 457926
---
 src/xcursortheme.cpp | 40 ++++++++++++++++++++++++++++------------
 1 file changed, 28 insertions(+), 12 deletions(-)

diff --git a/src/xcursortheme.cpp b/src/xcursortheme.cpp
index 5017deac2e..2421739679 100644
--- a/src/xcursortheme.cpp
+++ b/src/xcursortheme.cpp
@@ -12,7 +12,9 @@
 
 #include <QDir>
 #include <QFile>
+#include <QSet>
 #include <QSharedData>
+#include <QStack>
 #include <QStandardPaths>
 
 namespace KWin
@@ -157,22 +159,36 @@ static QStringList searchPaths()
 void KXcursorThemePrivate::load(const QString &themeName, int size, qreal devicePixelRatio)
 {
     const QStringList paths = searchPaths();
-    QStringList inherits;
 
-    for (const QString &path : paths) {
-        const QDir dir(path + QLatin1Char('/') + themeName);
-        if (!dir.exists()) {
+    QStack<QString> stack;
+    QSet<QString> loaded;
+
+    stack.push(themeName);
+
+    while (!stack.isEmpty()) {
+        const QString themeName = stack.pop();
+        if (loaded.contains(themeName)) {
             continue;
         }
-        loadCursors(dir.filePath(QStringLiteral("cursors")), size, devicePixelRatio);
-        if (inherits.isEmpty()) {
-            const KConfig config(dir.filePath(QStringLiteral("index.theme")), KConfig::NoGlobals);
-            inherits << KConfigGroup(&config, "Icon Theme").readEntry("Inherits", QStringList());
-        }
-    }
 
-    for (const QString &inherit : inherits) {
-        load(inherit, size, devicePixelRatio);
+        QStringList inherits;
+
+        for (const QString &path : paths) {
+            const QDir dir(path + QLatin1Char('/') + themeName);
+            if (!dir.exists()) {
+                continue;
+            }
+            loadCursors(dir.filePath(QStringLiteral("cursors")), size, devicePixelRatio);
+            if (inherits.isEmpty()) {
+                const KConfig config(dir.filePath(QStringLiteral("index.theme")), KConfig::NoGlobals);
+                inherits << KConfigGroup(&config, "Icon Theme").readEntry("Inherits", QStringList());
+            }
+        }
+
+        loaded.insert(themeName);
+        for (auto it = inherits.crbegin(); it != inherits.crend(); ++it) {
+            stack.push(*it);
+        }
     }
 }