baseline: Fix incorrect exit after invalid jump

To handle invalid jump the implementation targets the byte just after
the official code length. For padded code this byte may be uninitialized
push data causing unpredictable behavior. The fix is to also init this
byte to OP_STOP.

CHANGELOG.md

@@ -6,6 +6,14 @@ The format is based on [Keep a Changelog],
 and this project adheres to [Semantic Versioning].
 
 
+## [0.8.1] — unreleased
+
+### Fixed
+
+- baseline: Fix incorrect exit after invalid jump.
+  [#370](https://github.com/ethereum/evmone/pull/370)
+
+
 ## [0.8.0] — 2021-07-01
 
 ## Added
@@ -265,6 +273,7 @@ It delivers fully-compatible and high-speed EVM implementation.
 - The [intx 0.2.0](https://github.com/chfast/intx/releases/tag/v0.2.0) library is used for 256-bit precision arithmetic. 
 
 
+[0.8.1]: https://github.com/ethereum/evmone/compare/v0.8.0..release/v0.8.0
 [0.8.0]: https://github.com/ethereum/evmone/releases/tag/v0.8.0
 [0.7.0]: https://github.com/ethereum/evmone/releases/tag/v0.7.0
 [0.6.0]: https://github.com/ethereum/evmone/releases/tag/v0.6.0

lib/evmone/baseline.cpp

@@ -35,7 +35,8 @@ CodeAnalysis analyze(const uint8_t* code, size_t code_size)
     // Using "raw" new operator instead of std::make_unique() to get uninitialized array.
     std::unique_ptr<uint8_t[]> padded_code{new uint8_t[i + 1]};  // +1 for the final STOP.
     std::copy_n(code, code_size, padded_code.get());
-    padded_code[i] = OP_STOP;  // Set final STOP at the code end.
+    padded_code[code_size] = OP_STOP;  // Used to terminate invalid jumps, see op_jump().
+    padded_code[i] = OP_STOP;  // Set final STOP at the code end - guarantees loop termination.
 
     // TODO: Using fixed-size padding of 33, the padded code buffer and jumpdest bitmap can be
     //       created with single allocation.