EH: fix validation of delegate opcode

cf. bytecodealliance#1884 (comment)

core/iwasm/interpreter/wasm_loader.c

@@ -7129,6 +7129,40 @@ check_branch_block(WASMLoaderContext *loader_ctx, uint8 **p_buf, uint8 *buf_end,
  return NULL;
 }
 
+#if WASM_ENABLE_EXCE_HANDLING != 0
+static BranchBlock *
+check_branch_block_for_delegate(WASMLoaderContext *loader_ctx, uint8 **p_buf,
+ uint8 *buf_end, char *error_buf,
+ uint32 error_buf_size)
+{
+ uint8 *p = *p_buf, *p_end = buf_end;
+ BranchBlock *frame_csp_tmp;
+ uint32 depth;
+
+ read_leb_uint32(p, p_end, depth);
+ /*
+ * Note: "delegate 0" means the surrounding block, not the
+ * try-delegate block itself.
+ *
+ * Note: the caller hasn't popped the try-delegate frame yet.
+ */
+ bh_assert(loader_ctx->csp_num > 0);
+ if (loader_ctx->csp_num - 1 <= depth) {
+ set_error_buf(error_buf, error_buf_size, "unknown delegate label");
+ goto fail;
+ }
+ frame_csp_tmp = loader_ctx->frame_csp - depth - 2;
+#if WASM_ENABLE_FAST_INTERP != 0
+ emit_br_info(frame_csp_tmp);
+#endif
+
+ *p_buf = p;
+ return frame_csp_tmp;
+fail:
+ return NULL;
+}
+#endif
+
 static bool
 check_block_stack(WASMLoaderContext *loader_ctx, BranchBlock *block,
  char *error_buf, uint32 error_buf_size)
@@ -7831,16 +7865,10 @@ wasm_loader_prepare_bytecode(WASMModule *module, WASMFunction *func,
  case WASM_OP_DELEGATE:
  {
  /* check target block is valid */
- if (!(frame_csp_tmp = check_branch_block(
+ if (!(frame_csp_tmp = check_branch_block_for_delegate(
  loader_ctx, &p, p_end, error_buf, error_buf_size)))
  goto fail;
 
- /* valid types */
- if (LABEL_TYPE_TRY != frame_csp_tmp->label_type) {
- snprintf(error_buf, error_buf_size, "unknown label");
- goto fail;
- }
-
  BranchBlock *cur_block = loader_ctx->frame_csp - 1;
  uint8 label_type = cur_block->label_type;