From a2f678d3552aaaaa8d6f480cf5f2fbc849f376c3 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Mon, 7 May 2018 11:18:27 -0700
Subject: [PATCH] Bugfix: the end of a reorged chain is invalid when connect
 fails

Introduced in 4e0eed88acdd41826868c151373068bfad18b84d

When an invalid block is found during a reorg, we know the last of the blocks in
the was-to-be-connected chain is invalid, but not necessarily the first. As
vpIndexToConnect is ordered in decreasing height, the end of the reorg is the
front of the vector, and not the back.

This only affected the warning system.
---
 src/validation.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/validation.cpp b/src/validation.cpp
index fc1f6477d5..8a941561bb 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2551,8 +2551,9 @@ bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainPar
             if (!ConnectTip(state, chainparams, pindexConnect, pindexConnect == pindexMostWork ? pblock : std::shared_ptr<const CBlock>(), connectTrace, disconnectpool)) {
                 if (state.IsInvalid()) {
                     // The block violates a consensus rule.
-                    if (!state.CorruptionPossible())
-                        InvalidChainFound(vpindexToConnect.back());
+                    if (!state.CorruptionPossible()) {
+                        InvalidChainFound(vpindexToConnect.front());
+                    }
                     state = CValidationState();
                     fInvalidFound = true;
                     fContinue = false;