From 68f72955001da29cb5b7dd5a5f17e4df7357f7fb Mon Sep 17 00:00:00 2001
From: Vladimir Golovnev <glassez@yandex.ru>
Date: Sun, 15 Dec 2024 17:50:19 +0300
Subject: [PATCH] Avoid race condition when update tracker entries

PR #21995.
---
 src/base/bittorrent/sessionimpl.cpp | 12 +++++++++---
 src/base/bittorrent/sessionimpl.h   |  2 ++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/base/bittorrent/sessionimpl.cpp b/src/base/bittorrent/sessionimpl.cpp
index 26ae301b4412..edd6cc69607b 100644
--- a/src/base/bittorrent/sessionimpl.cpp
+++ b/src/base/bittorrent/sessionimpl.cpp
@@ -66,6 +66,7 @@
 #include <QJsonDocument>
 #include <QJsonObject>
 #include <QJsonValue>
+#include <QMutexLocker>
 #include <QNetworkAddressEntry>
 #include <QNetworkInterface>
 #include <QRegularExpression>
@@ -6201,6 +6202,8 @@ void SessionImpl::handleTrackerAlert(const lt::tracker_alert *alert)
     if (!torrent)
         return;
 
+    [[maybe_unused]] const QMutexLocker updatedTrackerStatusesLocker {&m_updatedTrackerStatusesMutex};
+
     const auto prevSize = m_updatedTrackerStatuses.size();
     QMap<int, int> &updateInfo = m_updatedTrackerStatuses[torrent->nativeHandle()][std::string(alert->tracker_url())][alert->local_endpoint];
     if (prevSize < m_updatedTrackerStatuses.size())
@@ -6297,14 +6300,17 @@ void SessionImpl::updateTrackerEntryStatuses(lt::torrent_handle torrentHandle)
         try
         {
             std::vector<lt::announce_entry> nativeTrackers = torrentHandle.trackers();
-            invoke([this, torrentHandle, nativeTrackers = std::move(nativeTrackers)]
+
+            QMutexLocker updatedTrackerStatusesLocker {&m_updatedTrackerStatusesMutex};
+            QHash<std::string, QHash<lt::tcp::endpoint, QMap<int, int>>> updatedTrackers = m_updatedTrackerStatuses.take(torrentHandle);
+            updatedTrackerStatusesLocker.unlock();
+
+            invoke([this, torrentHandle, nativeTrackers = std::move(nativeTrackers), updatedTrackers = std::move(updatedTrackers)]
             {
                 TorrentImpl *torrent = m_torrents.value(torrentHandle.info_hash());
                 if (!torrent || torrent->isStopped())
                     return;
 
-                QHash<std::string, QHash<lt::tcp::endpoint, QMap<int, int>>> updatedTrackers = m_updatedTrackerStatuses.take(torrentHandle);
-
                 QHash<QString, TrackerEntryStatus> trackers;
                 trackers.reserve(updatedTrackers.size());
                 for (const lt::announce_entry &announceEntry : nativeTrackers)
diff --git a/src/base/bittorrent/sessionimpl.h b/src/base/bittorrent/sessionimpl.h
index 4f35c59c2918..20f6558f5b7f 100644
--- a/src/base/bittorrent/sessionimpl.h
+++ b/src/base/bittorrent/sessionimpl.h
@@ -41,6 +41,7 @@
 #include <QElapsedTimer>
 #include <QHash>
 #include <QMap>
+#include <QMutex>
 #include <QPointer>
 #include <QSet>
 #include <QVector>
@@ -793,6 +794,7 @@ namespace BitTorrent
         // This field holds amounts of peers reported by trackers in their responses to announces
         // (torrent.tracker_name.tracker_local_endpoint.protocol_version.num_peers)
         QHash<lt::torrent_handle, QHash<std::string, QHash<lt::tcp::endpoint, QMap<int, int>>>> m_updatedTrackerStatuses;
+        QMutex m_updatedTrackerStatusesMutex;
 
         // I/O errored torrents
         QSet<TorrentID> m_recentErroredTorrents;