From b08f8bd1b042c0a9c49f34694885365f4372c345 Mon Sep 17 00:00:00 2001
From: Justin Starry <justin@solana.com>
Date: Wed, 30 Jun 2021 13:50:55 -0500
Subject: [PATCH] Fail simulation if transaction contains duplicate accounts
 (#18304)

---
 runtime/src/bank.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/runtime/src/bank.rs b/runtime/src/bank.rs
index d80525c785..cd9087816a 100644
--- a/runtime/src/bank.rs
+++ b/runtime/src/bank.rs
@@ -2616,8 +2616,17 @@ impl Bank {
         &'a self,
         tx: &'b Transaction,
     ) -> TransactionBatch<'a, 'b> {
+        let check_transaction = |tx: &Transaction| -> Result<()> {
+            tx.sanitize().map_err(TransactionError::from)?;
+            if Accounts::has_duplicates(&tx.message.account_keys) {
+                Err(TransactionError::AccountLoadedTwice)
+            } else {
+                Ok(())
+            }
+        };
+
         let mut batch = TransactionBatch::new(
-            vec![tx.sanitize().map_err(|e| e.into())],
+            vec![check_transaction(tx)],
             self,
             Cow::Owned(vec![HashedTransaction::from(tx)]),
         );