From 99a6b699cd650f13d7200d344bf5e2d4b45b20ac Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Wed, 26 Jan 2022 16:58:32 +0200
Subject: [PATCH] Fix race condition for SetBannedSetDirty() calls

Another thread can `SetBannedSetDirty(true)` while `CBanDB::Write()`
call being executed. The following `SetBannedSetDirty(false)`
effectively makes `m_is_dirty` flag value inconsistent with the actual
`m_banned` state. Such behavior can result in data loss, e.g., during
shutdown.
---
 src/banman.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/banman.cpp b/src/banman.cpp
index 87c1bbc89e2..b28e3f7f7cc 100644
--- a/src/banman.cpp
+++ b/src/banman.cpp
@@ -49,11 +49,12 @@ void BanMan::DumpBanlist()
         SweepBanned();
         if (!BannedSetIsDirty()) return;
         banmap = m_banned;
+        SetBannedSetDirty(false);
     }
 
     int64_t n_start = GetTimeMillis();
-    if (m_ban_db.Write(banmap)) {
-        SetBannedSetDirty(false);
+    if (!m_ban_db.Write(banmap)) {
+        SetBannedSetDirty(true);
     }
 
     LogPrint(BCLog::NET, "Flushed %d banned node addresses/subnets to disk  %dms\n", banmap.size(),