gpu_fuzzer: gracefully handle over-the-limit input

gpu/command_buffer/tests/fuzzer_main.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <vector>
 
 #include "base/at_exit.h"
@@ skipping 120 matching lines @@
 
   ~CommandBufferSetup() {
     sync_point_client_ = nullptr;
     if (sync_point_order_data_) {
       sync_point_order_data_->Destroy();
       sync_point_order_data_ = nullptr;
     }
   }
 
   void RunCommandBuffer(const uint8_t* data, size_t size) {
-    InitDecoder();
     // The commands are flushed at a uint32_t granularity. If the data is not
     // a full command, we zero-pad it.
     size_t padded_size = (size + 3) & ~3;
+    // crbug.com/638836 The -max_len argument is sometimes not respected, so the
+    // fuzzer may give us too much data. Bail ASAP in that case.
+    if (padded_size > kCommandBufferSize)
+      return;
+
+    InitDecoder();
     size_t buffer_size = buffer_->size();
     CHECK_LE(padded_size, buffer_size);
     command_buffer_->SetGetBuffer(buffer_id_);
     auto* memory = static_cast<char*>(buffer_->memory());
     memcpy(memory, data, size);
     if (size < buffer_size)
       memset(memory + size, 0, buffer_size - size);
     command_buffer_->Flush(padded_size / 4);
     ResetDecoder();
   }
@@ skipping 96 matching lines @@
 
 static gpu::CommandBufferSetup& GetSetup() {
   static gpu::CommandBufferSetup setup;
   return setup;
 }
 
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   GetSetup().RunCommandBuffer(data, size);
   return 0;
 }