Fix sub_bytes code

fuel-vm/src/interpreter/blockchain.rs

@@ -508,11 +508,8 @@ where
                 .into_owned()
                 .into();
         let contract_len = contract_bytes.len();
-        let start = contract_offset;
-        let finish = contract_offset
-            .checked_add(length_unpadded)
-            .ok_or(PanicReason::MemoryOverflow)?;
-        let contract_sub_bytes = &contract_bytes[start..finish];
+        let contract_sub_bytes =
+            read_contract_bytes(&contract_bytes, contract_offset, length_unpadded);
 
         // Mark stack space as allocated
         let new_stack = dst_range.words().end;
@@ -522,7 +519,7 @@ where
         // Copy the code. Ownership checks are not used as the stack is adjusted above.
         copy_from_slice_zero_fill_noownerchecks(
             self.memory,
-            contract_sub_bytes,
+            &contract_sub_bytes,
             dst_range.start,
             contract_offset,
             length,
@@ -557,6 +554,18 @@ where
     }
 }
 
+/// Copy $rC bytes of code starting at $rB for contract.
+/// If $rC is greater than the code size, zero bytes are filled in.
+fn read_contract_bytes(contract_bytes: &[u8], offset: usize, length: usize) -> Vec<u8> {
+    let mut buf = vec![0u8; length];
+    if contract_bytes.len() > offset {
+        for (i, val) in contract_bytes[offset..].iter().enumerate().take(length) {
+            buf[i] = *val;
+        }
+    };
+    buf
+}
+
 struct BurnCtx<'vm, S> {
     storage: &'vm mut S,
     context: &'vm Context,