Fix account migration from before revision (#285)

evm_loader/lib/src/account_update.rs

@@ -13,13 +13,16 @@ fn from_before_revision(account: &mut Account, new_tag: u8) {
     const PREFIX_BEFORE: usize = ACCOUNT_PREFIX_LEN_BEFORE_REVISION;
     const PREFIX_AFTER: usize = ACCOUNT_PREFIX_LEN;
 
-    assert!(account.data.len() > PREFIX_BEFORE);
+    let data: &mut Vec<u8> = &mut account.data;
 
-    let required_len = account.data.len() + PREFIX_AFTER - PREFIX_BEFORE;
-    account.data.resize(required_len, 0);
+    assert!(data.len() > PREFIX_BEFORE);
+    let data_len = data.len() - PREFIX_BEFORE;
 
-    account.data.copy_within(PREFIX_BEFORE.., PREFIX_AFTER);
-    account.data[0] = new_tag;
+    let required_len = data.len() + PREFIX_AFTER - PREFIX_BEFORE;
+    data.resize(required_len, 0);
+
+    data.copy_within(PREFIX_BEFORE..(PREFIX_BEFORE + data_len), PREFIX_AFTER);
+    data[0] = new_tag;
 }
 
 pub fn update_account(program_id: &Pubkey, key: &Pubkey, account: &mut Account) -> NeonResult<()> {

evm_loader/program/src/account/legacy/update.rs

@@ -17,18 +17,21 @@ pub fn from_before_revision<'a>(
     const PREFIX_BEFORE: usize = ACCOUNT_PREFIX_LEN_BEFORE_REVISION;
     const PREFIX_AFTER: usize = ACCOUNT_PREFIX_LEN;
 
+    assert!(account.data_len() > PREFIX_BEFORE);
+    let data_len = account.data_len() - PREFIX_BEFORE;
+
     let required_len = account.data_len() + PREFIX_AFTER - PREFIX_BEFORE;
     account.realloc(required_len, false)?;
 
-    let minimum_balance = rent.minimum_balance(account.data_len());
+    let minimum_balance = rent.minimum_balance(required_len);
     if account.lamports() < minimum_balance {
         let required_lamports = minimum_balance - account.lamports();
         system.transfer(operator, account, required_lamports)?;
     }
 
     let mut account_data = account.try_borrow_mut_data()?;
+    account_data.copy_within(PREFIX_BEFORE..(PREFIX_BEFORE + data_len), PREFIX_AFTER);
     account_data[0] = new_tag;
-    account_data.copy_within(PREFIX_BEFORE.., PREFIX_AFTER);
 
     Ok(())
 }