Fix - Interpreter check_pc! (#643)

* Adds test_err_callx_oob_max.

* Removes unnecessary debug mode arithmetic guard.

Author: Lichtso

src/interpreter.rs

@@ -67,7 +67,11 @@ macro_rules! check_pc {
     ($self:expr, $next_pc:ident, $target_pc:expr) => {
         if ($target_pc as usize)
             .checked_mul(ebpf::INSN_SIZE)
-            .and_then(|offset| $self.program.get(offset..offset + ebpf::INSN_SIZE))
+            .and_then(|offset| {
+                $self
+                    .program
+                    .get(offset..offset.saturating_add(ebpf::INSN_SIZE))
+            })
             .is_some()
         {
             $next_pc = $target_pc;

tests/execution.rs

@@ -2490,6 +2490,20 @@ fn test_err_callx_oob_high() {
     );
 }
 
+#[test]
+fn test_err_callx_oob_max() {
+    test_interpreter_and_jit_asm!(
+        "
+        mov64 r0, -0x8
+        hor64 r0, -0x1
+        callx r0
+        exit",
+        [],
+        TestContextObject::new(3),
+        ProgramResult::Err(EbpfError::CallOutsideTextSegment),
+    );
+}
+
 #[test]
 fn test_callx_unaligned_text_section() {
     test_interpreter_and_jit_elf!(