evm: check JUMPDEST only before real jump in JUMPI

cdump · Dec 19, 2023 · 231c994 · 231c994
1 parent 81c6b1f
commit 231c994
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Showing 2 changed files with 6 additions and 6 deletions.
diff --git a/evmole/evm/vm.py b/evmole/evm/vm.py
@@ -80,13 +80,13 @@ def _exec_opcode(self, op: OpCode) -> tuple[int, *tuple[Any, ...]]:
 
             case op if op in {Op.JUMP, Op.JUMPI}:
                 s0 = self.stack.pop_uint()
-                if s0 >= len(self.code) or self.code[s0] != Op.JUMPDEST:
-                    raise BadJumpDestError(f'pos {s0}')
                 if op == Op.JUMPI:
                     s1 = self.stack.pop_uint()
                     if s1 == 0:
                         self.pc += 1
                         return (10,)
+                if s0 >= len(self.code) or self.code[s0] != Op.JUMPDEST:
+                    raise BadJumpDestError(f'pos {s0}')
                 self.pc = s0
                 return (8 if op == Op.JUMP else 10,)
 

diff --git a/js/src/evm/vm.js b/js/src/evm/vm.js
@@ -97,17 +97,17 @@ export class Vm {
       case Op.JUMP:
       case Op.JUMPI: {
         const s0 = Number(this.stack.pop_uint())
-        if (s0 >= this.code.length || this.code[s0] != Op.JUMPDEST) {
-          throw new BadJumpDestError(`pos ${s0}`)
-        }
         if (op == Op.JUMPI) {
           const s1 = this.stack.pop_uint()
           if (s1 == 0n) {
             this.pc += 1
             return [10]
           }
         }
-        this.pc = Number(s0)
+        if (s0 >= this.code.length || this.code[s0] != Op.JUMPDEST) {
+          throw new BadJumpDestError(`pos ${s0}`)
+        }
+        this.pc = s0
         return [op === Op.JUMP ? 8 : 10]
       }