v1.17: bank: do not remove trailing 0 bytes from return data (backpor…

…t of solana-labs#33639) (solana-labs#33685)

bank: do not remove trailing 0 bytes from return data (solana-labs#33639)

This is creating havoc for Solang, as the return data is borsh encoded
and therefore `u64` values like 0x100 get truncated.

(cherry picked from commit 4751199)

Co-authored-by: Sean Young <[email protected]>

runtime/src/bank.rs

@@ -4951,7 +4951,7 @@ impl Bank {
 
         let ExecutionRecord {
             accounts,
-            mut return_data,
+            return_data,
             touched_account_count,
             accounts_resize_delta,
         } = transaction_context.into();
@@ -4981,14 +4981,8 @@ impl Bank {
             accounts_data_len_delta = status.as_ref().map_or(0, |_| accounts_resize_delta);
         }
 
-        let return_data = if enable_return_data_recording {
-            if let Some(end_index) = return_data.data.iter().rposition(|&x| x != 0) {
-                let end_index = end_index.saturating_add(1);
-                return_data.data.truncate(end_index);
-                Some(return_data)
-            } else {
-                None
-            }
+        let return_data = if enable_return_data_recording && !return_data.data.is_empty() {
+            Some(return_data)
         } else {
             None
         };

runtime/src/bank/tests.rs

@@ -9712,9 +9712,9 @@ fn test_tx_return_data() {
         let mut return_data = [0u8; MAX_RETURN_DATA];
         if !instruction_data.is_empty() {
             let index = usize::from_le_bytes(instruction_data.try_into().unwrap());
-            return_data[index] = 1;
+            return_data[index / 2] = 1;
             transaction_context
-                .set_return_data(mock_program_id, return_data.to_vec())
+                .set_return_data(mock_program_id, return_data[..index + 1].to_vec())
                 .unwrap();
         }
         Ok(())
@@ -9766,8 +9766,9 @@ fn test_tx_return_data() {
         if let Some(index) = index {
             let return_data = return_data.unwrap();
             assert_eq!(return_data.program_id, mock_program_id);
-            let mut expected_data = vec![0u8; index];
-            expected_data.push(1u8);
+            let mut expected_data = vec![0u8; index + 1];
+            // include some trailing zeros
+            expected_data[index / 2] = 1;
             assert_eq!(return_data.data, expected_data);
         } else {
             assert!(return_data.is_none());