[wasm] Fix check failure on invalid name section

src/wasm/module-decoder.cc

 // Copyright 2015 the V8 project 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 "src/wasm/module-decoder.h"
 
 #include "src/base/functional.h"
 #include "src/base/platform/platform.h"
 #include "src/flags.h"
 #include "src/macro-assembler.h"
@@ skipping 602 matching lines @@
       // TODO(titzer): find a way to report name errors as warnings.
       // Use an inner decoder so that errors don't fail the outer decoder.
       Decoder inner(start_, pc_, end_);
       uint32_t functions_count = inner.consume_u32v("functions count");
 
       for (uint32_t i = 0; inner.ok() && i < functions_count; ++i) {
         uint32_t function_name_length = 0;
         uint32_t name_offset =
             consume_string(inner, &function_name_length, false);
         uint32_t func_index = i;
-        if (func_index < module->functions.size()) {
+        if (inner.ok() && func_index < module->functions.size()) {

[bradn, 2017/01/25 11:18:05]

Ah I see.
Kind of goofy how this section is speced (i.e. can fail to validate but is still
ok).
Don't we need to back this out in the case that some later part of this section
fails?
I.e. we could end up with some names added but then fall over?

[titzer, 2017/01/25 11:53:29]

I'm OK with "best effort" if we just leave the names that did parse
successfully. I'm also OK clearing them, as it is probably just a simple loop
after this. But land away.

[Mircea Trofin, 2017/01/25 15:58:51]

We should take a stance though and propose a PR on the Spec. 

[Mircea Trofin, 2017/01/25 16:42:00]

Followed up with this PR, please take a look (includes a proposal for expected
behavior surrounding this section):

https://github.com/WebAssembly/design/pull/967/commits/c7ac091c4ab5488fe989d2...

           module->functions[func_index].name_offset = name_offset;
           module->functions[func_index].name_length = function_name_length;
         }
 
         uint32_t local_names_count = inner.consume_u32v("local names count");
         for (uint32_t j = 0; ok() && j < local_names_count; j++) {
           uint32_t length = inner.consume_u32v("string length");
           inner.consume_bytes(length, "string");
         }
       }
@@ skipping 660 matching lines @@
     result.push_back({section_start, name_offset, name_length, payload_offset,
                       payload_length, section_length});
   }
 
   return result;
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8