Fix - Interpreter ExceededMaxInstructions and ExecutionOverrun (#592

)

* Fixes EbpfError::ExecutionOverrun in interpreter.

* Fixes EbpfError::ExceededMaxInstructions in interpreter.

* Adds test coverage.

src/interpreter.rs

@@ -159,11 +159,14 @@ impl<'a, 'b, C: ContextObject> Interpreter<'a, 'b, C> {
     pub fn step(&mut self) -> bool {
         let config = &self.executable.get_config();
 
+        if config.enable_instruction_meter && self.vm.due_insn_count >= self.vm.previous_instruction_meter {
+            throw_error!(self, EbpfError::ExceededMaxInstructions);
+        }
         self.vm.due_insn_count += 1;
-        let mut next_pc = self.reg[11] + 1;
-        if next_pc as usize * ebpf::INSN_SIZE > self.program.len() {
+        if self.reg[11] as usize * ebpf::INSN_SIZE >= self.program.len() {
             throw_error!(self, EbpfError::ExecutionOverrun);
         }
+        let mut next_pc = self.reg[11] + 1;
         let mut insn = ebpf::get_insn_unchecked(self.program, self.reg[11] as usize);
         let dst = insn.dst as usize;
         let src = insn.src as usize;

tests/execution.rs

@@ -3499,6 +3499,15 @@ fn test_execution_overrun() {
         TestContextObject::new(1),
         ProgramResult::Err(EbpfError::ExceededMaxInstructions),
     );
+    test_interpreter_and_jit_asm!(
+        "
+        add r1, 0",
+        config.clone(),
+        [],
+        (),
+        TestContextObject::new(0),
+        ProgramResult::Err(EbpfError::ExceededMaxInstructions),
+    );
 }
 
 #[test]