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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The repro case is 1 byte, which seems implausible. There don't seem to be any changes to fonts within the regression range?

I can reproduce this on Goobuntu. msw@, would you be the right person to fix this?

No, my text rendering work has been for chrome browser ui, not the blink renderer (they're completely separate harfbuzz clients). Hopefully drott@ or eae@ can triage.

Behdad, are these more instances of https://github.com/behdad/harfbuzz/issues/474 ?

Yes. 

Downgrading this to same severity as  issue 696729  and removing ReleaseBlock-Stable.

Automatically applying components based on information from OWNERS files. If this seems incorrect, please apply the Test-Predator-Wrong-Components label.

For more information, please see https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.md.

The link referenced in the description is no longer valid.

 Issue 761694  has been merged into this issue.

ClusterFuzz has detected this issue as fixed in range 513517:513548.

Detailed report: https://clusterfuzz.com/testcase?key=5975138029010944

Fuzzer: libFuzzer_renderer_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Incorrect-function-pointer-type
Crash Address: 
Crash State:
  _hb_blob_destroy_user_data
  hb_blob_destroy
  hb_face_t::get_upem
  
Sanitizer: undefined (UBSAN)

Recommended Security Severity: Medium

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=496738:496798
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=513517:513548

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5975138029010944

See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reference.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 6020511204376576 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