Don't read unlimited data from files

It now guards against reading infinite files such as `/dev/zero`.
And most readings are bound with a (lax) limit.
As a side effect, more checking are done when reading a file and
overall the reading procedure is more robust.

PR #19095.

src/base/rss/feed_serializer.cpp

@@ -31,7 +31,6 @@
 
 #include "feed_serializer.h"
 
-#include <QFile>
 #include <QJsonArray>
 #include <QJsonDocument>
 #include <QJsonObject>
@@ -46,23 +45,21 @@ const int ARTICLEDATALIST_TYPEID = qRegisterMetaType<QVector<QVariantHash>>();
 
 void RSS::Private::FeedSerializer::load(const Path &dataFileName, const QString &url)
 {
-    QFile file {dataFileName.data()};
+    const int fileMaxSize = 10 * 1024 * 1024;
+    const auto readResult = Utils::IO::readFile(dataFileName, fileMaxSize);
+    if (!readResult)
+    {
+        if (readResult.error().status == Utils::IO::ReadError::NotExist)
+        {
+            emit loadingFinished({});
+            return;
+        }
 
-    if (!file.exists())
-    {
-        emit loadingFinished({});
-    }
-    else if (file.open(QFile::ReadOnly))
-    {
-        emit loadingFinished(loadArticles(file.readAll(), url));
-        file.close();
-    }
-    else
-    {
-        LogMsg(tr("Couldn't read RSS Session data from %1. Error: %2")
-               .arg(dataFileName.toString(), file.errorString())
-               , Log::WARNING);
+        LogMsg(tr("Failed to read RSS session data. %1").arg(readResult.error().message), Log::WARNING);
+        return;
     }
+
+    emit loadingFinished(loadArticles(readResult.value(), url));
 }
 
 void RSS::Private::FeedSerializer::store(const Path &dataFileName, const QVector<QVariantHash> &articlesData)

src/base/rss/rss_autodownloader.cpp

@@ -48,6 +48,7 @@
 #include "../logger.h"
 #include "../profile.h"
 #include "../utils/fs.h"
+#include "../utils/io.h"
 #include "rss_article.h"
 #include "rss_autodownloadrule.h"
 #include "rss_feed.h"
@@ -493,21 +494,21 @@ void AutoDownloader::processJob(const QSharedPointer<ProcessingJob> &job)
 
 void AutoDownloader::load()
 {
-    QFile rulesFile {(m_fileStorage->storageDir() / Path(RULES_FILE_NAME)).data()};
+    const qint64 maxFileSize = 10 * 1024 * 1024;
+    const auto readResult = Utils::IO::readFile((m_fileStorage->storageDir() / Path(RULES_FILE_NAME)), maxFileSize);
+    if (!readResult)
+    {
+        if (readResult.error().status == Utils::IO::ReadError::NotExist)
+        {
+            loadRulesLegacy();
+            return;
+        }
 
-    if (!rulesFile.exists())
-    {
-        loadRulesLegacy();
-    }
-    else if (rulesFile.open(QFile::ReadOnly))
-    {
-        loadRules(rulesFile.readAll());
-    }
-    else
-    {
-        LogMsg(tr("Couldn't read RSS AutoDownloader rules from %1. Error: %2")
-                .arg(rulesFile.fileName(), rulesFile.errorString()), Log::CRITICAL);
+        LogMsg((tr("Failed to read RSS AutoDownloader rules. %1").arg(readResult.error().message)), Log::WARNING);
+        return;
     }
+
+    loadRules(readResult.value());
 }
 
 void AutoDownloader::loadRules(const QByteArray &data)

src/base/rss/rss_session.cpp

@@ -45,6 +45,7 @@
 #include "../profile.h"
 #include "../settingsstorage.h"
 #include "../utils/fs.h"
+#include "../utils/io.h"
 #include "rss_article.h"
 #include "rss_feed.h"
 #include "rss_folder.h"
@@ -261,33 +262,35 @@ Item *Session::itemByPath(const QString &path) const
 
 void Session::load()
 {
-    QFile itemsFile {(m_confFileStorage->storageDir() / Path(FEEDS_FILE_NAME)).data()};
-    if (!itemsFile.exists())
-    {
-        loadLegacy();
-        return;
-    }
+    const int fileMaxSize = 10 * 1024 * 1024;
+    const Path path = m_confFileStorage->storageDir() / Path(FEEDS_FILE_NAME);
 
-    if (!itemsFile.open(QFile::ReadOnly))
+    const auto readResult = Utils::IO::readFile(path, fileMaxSize);
+    if (!readResult)
     {
-        LogMsg(tr("Couldn't read RSS session data. File: \"%1\". Error: \"%2\"")
-            .arg(itemsFile.fileName(), itemsFile.errorString()), Log::WARNING);
+        if (readResult.error().status == Utils::IO::ReadError::NotExist)
+        {
+            loadLegacy();
+            return;
+        }
+
+        LogMsg(tr("Failed to read RSS session data. %1").arg(readResult.error().message), Log::WARNING);
         return;
     }
 
     QJsonParseError jsonError;
-    const QJsonDocument jsonDoc = QJsonDocument::fromJson(itemsFile.readAll(), &jsonError);
+    const QJsonDocument jsonDoc = QJsonDocument::fromJson(readResult.value(), &jsonError);
     if (jsonError.error != QJsonParseError::NoError)
     {
-        LogMsg(tr("Couldn't parse RSS session data. File: \"%1\". Error: \"%2\"")
-            .arg(itemsFile.fileName(), jsonError.errorString()), Log::WARNING);
+        LogMsg(tr("Failed to parse RSS session data. File: \"%1\". Error: \"%2\"")
+            .arg(path.toString(), jsonError.errorString()), Log::WARNING);
         return;
     }
 
     if (!jsonDoc.isObject())
     {
-        LogMsg(tr("Couldn't load RSS session data. File: \"%1\". Error: Invalid data format.")
-            .arg(itemsFile.fileName()), Log::WARNING);
+        LogMsg(tr("Failed to load RSS session data. File: \"%1\". Error: \"Invalid data format.\"")
+            .arg(path.toString()), Log::WARNING);
         return;
     }