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.

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

Looks to have been caused by https://chromium-review.googlesource.com/583854

URGENT - PTAL.
Your bug is labelled as Stable ReleaseBlock, pls make sure to land the fix and get it merged into the M61 branch #3163 ASAP to have enough baking time in Beta before Stable promotion. Thank you!

Know that this issue shouldn't block the release?  Remove the ReleaseBlock-Stable label.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/620fd0052d8f7042ceb376eec6d0845311282305

commit 620fd0052d8f7042ceb376eec6d0845311282305
Author: Adrienne Walker <enne@chromium.org>
Date: Thu Jul 27 17:06:46 2017

Fix uninitialized use in PaintOpReader::Read(SkData)

If ReadSimple fails, then size_t bytes is uninitialized.

Bug:  748942 
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I283774372d84bd6266f1b10720093a6083409f73
Reviewed-on: https://chromium-review.googlesource.com/587650
Reviewed-by: Khushal <khushalsagar@chromium.org>
Commit-Queue: enne <enne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#489986}
[modify] https://crrev.com/620fd0052d8f7042ceb376eec6d0845311282305/cc/paint/paint_op_reader.cc

ClusterFuzz has detected this issue as fixed in range 489908:490016.

Detailed report: https://clusterfuzz.com/testcase?key=6059414598713344

Fuzzer: libFuzzer_paint_op_buffer_fuzzer
Job Type: libfuzzer_chrome_msan
Platform Id: linux

Crash Type: Use-of-uninitialized-value
Crash Address: 
Crash State:
  cc::PaintOpReader::Read
  cc::AnnotateOp::Deserialize
  cc::PaintOp::Deserialize
  
Sanitizer: memory (MSAN)

Recommended Security Severity: Medium

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_msan&range=489402:489491
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_msan&range=489908:490016

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6059414598713344


See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reproducing.md for more information.

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

ClusterFuzz testcase 6059414598713344 is verified as fixed, so closing issue as verified.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.

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