From d24735b2173f4757cedd7bb54036f465d8c5d9ed Mon Sep 17 00:00:00 2001
From: John Preston <johnprestonmail@gmail.com>
Date: Fri, 17 Jan 2020 17:45:43 +0300
Subject: [PATCH] Fix possible crash in CDN file loading.

---
 Telegram/SourceFiles/storage/download_manager_mtproto.cpp | 7 +++++++
 Telegram/SourceFiles/storage/download_manager_mtproto.h   | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Telegram/SourceFiles/storage/download_manager_mtproto.cpp b/Telegram/SourceFiles/storage/download_manager_mtproto.cpp
index 9d6f25be4..02df6fa4e 100644
--- a/Telegram/SourceFiles/storage/download_manager_mtproto.cpp
+++ b/Telegram/SourceFiles/storage/download_manager_mtproto.cpp
@@ -487,6 +487,13 @@ void DownloadMtprotoTask::removeSession(int sessionIndex) {
 			redirect.push_back({ requestId, requestData.offset });
 		}
 	}
+	for (auto &[requestData, bytes] : _cdnUncheckedParts) {
+		if (requestData.sessionIndex == sessionIndex) {
+			const auto newIndex = _owner->chooseSessionIndex(dcId());
+			Assert(newIndex < sessionIndex);
+			requestData.sessionIndex = newIndex;
+		}
+	}
 	for (const auto &[requestId, offset] : redirect) {
 		cancelRequest(requestId);
 		const auto newIndex = _owner->chooseSessionIndex(dcId());
diff --git a/Telegram/SourceFiles/storage/download_manager_mtproto.h b/Telegram/SourceFiles/storage/download_manager_mtproto.h
index de342fd68..41f91b32c 100644
--- a/Telegram/SourceFiles/storage/download_manager_mtproto.h
+++ b/Telegram/SourceFiles/storage/download_manager_mtproto.h
@@ -163,7 +163,7 @@ protected:
 private:
 	struct RequestData {
 		int offset = 0;
-		int sessionIndex = 0;
+		mutable int sessionIndex = 0;
 		int requestedInSession = 0;
 		crl::time sent = 0;