From fec99efb8f12ee9d12f777f59d09549c9caa5715 Mon Sep 17 00:00:00 2001
From: Andrew Poelstra <apoelstra@wpsoftware.net>
Date: Tue, 15 Dec 2020 00:38:34 +0000
Subject: [PATCH] fix invalid memory access that I added when merging
 descriptor wallets

Thanks, ubsan + fuzzer!
---
 src/script/sign.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 390b9f2b04..940bd6a65e 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -506,11 +506,11 @@ bool SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore,
             prevTxOut = GetPeginOutputFromWitness(mtx.witness.vtxinwit[i].m_pegin_witness);
         } else {
             auto coin = coins.find(txin.prevout);
-            prevTxOut = coin->second.out;
             if (coin == coins.end() || coin->second.IsSpent()) {
                 input_errors[i] = "Input not found or already spent";
                 continue;
             }
+            prevTxOut = coin->second.out;
         }
 
         const CScript& prevPubKey = prevTxOut.scriptPubKey;