From f146c92e8896bf4252c61c3debc7996a9f77986e Mon Sep 17 00:00:00 2001
From: Michael Vines <mvines@gmail.com>
Date: Thu, 5 Mar 2020 09:14:40 -0700
Subject: [PATCH] Always and fully normalize stored 0-lamport accts. (#8657)

---
 runtime/src/accounts_db.rs                  | 13 ++--
 runtime/src/system_instruction_processor.rs | 73 +++++++++++++++++++++
 2 files changed, 81 insertions(+), 5 deletions(-)

diff --git a/runtime/src/accounts_db.rs b/runtime/src/accounts_db.rs
index e8fd83375..933c6d092 100644
--- a/runtime/src/accounts_db.rs
+++ b/runtime/src/accounts_db.rs
@@ -1033,22 +1033,25 @@ impl AccountsDB {
         accounts: &[(&Pubkey, &Account)],
         hashes: &[Hash],
     ) -> Vec<AccountInfo> {
+        let default_account = Account::default();
+
         let with_meta: Vec<(StoredMeta, &Account)> = accounts
             .iter()
             .map(|(pubkey, account)| {
                 let write_version = self.write_version.fetch_add(1, Ordering::Relaxed) as u64;
-                let data_len = if account.lamports == 0 {
-                    0
+                let account = if account.lamports == 0 {
+                    &default_account
                 } else {
-                    account.data.len() as u64
+                    *account
                 };
+                let data_len = account.data.len() as u64;
+
                 let meta = StoredMeta {
                     write_version,
                     pubkey: **pubkey,
                     data_len,
                 };
-
-                (meta, *account)
+                (meta, account)
             })
             .collect();
         let mut infos: Vec<AccountInfo> = Vec::with_capacity(with_meta.len());
diff --git a/runtime/src/system_instruction_processor.rs b/runtime/src/system_instruction_processor.rs
index 945a11d11..4ae4d7587 100644
--- a/runtime/src/system_instruction_processor.rs
+++ b/runtime/src/system_instruction_processor.rs
@@ -341,6 +341,7 @@ mod tests {
         transaction::TransactionError,
     };
     use std::cell::RefCell;
+    use std::sync::Arc;
 
     impl From<Pubkey> for Address {
         fn from(address: Pubkey) -> Self {
@@ -942,6 +943,78 @@ mod tests {
             .is_ok());
     }
 
+    fn with_create_zero_lamport<F>(callback: F)
+    where
+        F: Fn(&Bank) -> (),
+    {
+        solana_logger::setup();
+
+        let alice_keypair = Keypair::new();
+        let bob_keypair = Keypair::new();
+
+        let alice_pubkey = alice_keypair.pubkey();
+        let bob_pubkey = bob_keypair.pubkey();
+
+        let program = Pubkey::new_rand();
+        let collector = Pubkey::new_rand();
+
+        let mint_lamports = 10000;
+        let len1 = 123;
+        let len2 = 456;
+
+        // create initial bank and fund the alice account
+        let (genesis_config, mint_keypair) = create_genesis_config(mint_lamports);
+        let bank = Arc::new(Bank::new(&genesis_config));
+        let bank_client = BankClient::new_shared(&bank);
+        bank_client
+            .transfer(mint_lamports, &mint_keypair, &alice_pubkey)
+            .unwrap();
+
+        // create zero-lamports account to be cleaned
+        let bank = Arc::new(Bank::new_from_parent(&bank, &collector, bank.slot() + 1));
+        let bank_client = BankClient::new_shared(&bank);
+        let ix = system_instruction::create_account(&alice_pubkey, &bob_pubkey, 0, len1, &program);
+        let message = Message::new(vec![ix]);
+        let r = bank_client.send_message(&[&alice_keypair, &bob_keypair], message);
+        assert!(r.is_ok());
+
+        // transfer some to bogus pubkey just to make previous bank (=slot) really cleanable
+        let bank = Arc::new(Bank::new_from_parent(&bank, &collector, bank.slot() + 1));
+        let bank_client = BankClient::new_shared(&bank);
+        bank_client
+            .transfer(50, &alice_keypair, &Pubkey::new_rand())
+            .unwrap();
+
+        // super fun time; callback chooses to .clean_accounts() or not
+        callback(&*bank);
+
+        // create a normal account at the same pubkey as the zero-lamports account
+        let bank = Arc::new(Bank::new_from_parent(&bank, &collector, bank.slot() + 1));
+        let bank_client = BankClient::new_shared(&bank);
+        let ix = system_instruction::create_account(&alice_pubkey, &bob_pubkey, 1, len2, &program);
+        let message = Message::new(vec![ix]);
+        let r = bank_client.send_message(&[&alice_keypair, &bob_keypair], message);
+        assert!(r.is_ok());
+    }
+
+    #[test]
+    fn test_create_zero_lamport_with_clean() {
+        with_create_zero_lamport(|bank| {
+            bank.squash();
+            // do clean and assert that it actually did its job
+            assert_eq!(3, bank.get_snapshot_storages().len());
+            bank.clean_accounts();
+            assert_eq!(2, bank.get_snapshot_storages().len());
+        });
+    }
+
+    #[test]
+    fn test_create_zero_lamport_without_clean() {
+        with_create_zero_lamport(|_| {
+            // just do nothing; this should behave identically with test_create_zero_lamport_with_clean
+        });
+    }
+
     #[test]
     fn test_assign_with_seed() {
         let (genesis_config, mint_keypair) = create_genesis_config(100);