This is a serious security regression. If you are not able to fix this quickly, please revert the change that introduced it.

If this doesn't affect a release branch, or has not been properly classified for severity, please update the Security_Impact or Security_Severity labels, and remove the ReleaseBlock label. To disable this altogether, apply ReleaseBlock-NA.

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titzer@chromium.org, would you mind take a look? Since your CL is the only one in the regression range. 

Feel free to re-assign. Thanks!

The following revision refers to this bug:
  https://chromium.googlesource.com/v8/v8.git/+/11484e7e9b83564a0e0f08f02dae9e81c9fc5910

commit 11484e7e9b83564a0e0f08f02dae9e81c9fc5910
Author: titzer <titzer@chromium.org>
Date: Mon Jul 10 13:49:34 2017

[wasm] Improve precision of slow DCHECK for WebAssembly-constructed internal objects.

BUG= chromium:740325 
R=ahaas@chromium.org,mlippautz@chromium.org

Review-Url: https://codereview.chromium.org/2972353002
Cr-Commit-Position: refs/heads/master@{#46518}

[modify] https://crrev.com/11484e7e9b83564a0e0f08f02dae9e81c9fc5910/src/objects.cc
[add] https://crrev.com/11484e7e9b83564a0e0f08f02dae9e81c9fc5910/test/mjsunit/asm/regress-740325.js

ClusterFuzz has detected this issue as fixed in range 46517:46518.

Detailed report: https://clusterfuzz.com/testcase?key=5327306519478272

Fuzzer: mbarbella_js_mutation
Job Type: linux_asan_d8_dbg
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  is_api_object in objects.cc
  v8::internal::JSObject::WasConstructedFromApiFunction
  v8::internal::JSObject::IsUnmodifiedApiObject
  
Sanitizer: address (ASAN)

Regressed: V8: 46474:46475
Fixed: V8: 46517:46518

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5327306519478272


See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

This bug has been closed for more than 14 weeks. Removing security view restrictions.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot