Nothing obvious in the regression range; the only SwiftShader roll is: https://swiftshader.googlesource.com/SwiftShader.git/+log/a0aa5fd..05bcbe6

capn@ could you please help triage?

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

Re #4: Issues of Security Severity Medium typically get a Pri-1 severity (https://chromium.googlesource.com/chromium/src/+/lkcr/docs/security/severity-guidelines.md). Is there a mitigating factor here that's not obvious and which also reduces the Security Severity?

This only affects the GPU process, which is where the (generally untrusted) graphics driver runs. Graphics driver crashes are common enough that we have a three-strikes mechanism to fall back to dedicated CPU based graphics and not use the GPU process.

Note that in general the graphics driver is a black box to us, but in the case of SwiftShader we have full source code and this recently added fuzzer is finding some edge cases to make it crash. It's still more robust that many of the GPU drivers though.

We'll make a coordinated attempt at fixing all of the issues found by this fuzzer in Q1, but for now I don't think these are P1 nor release blockers.

ClusterFuzz has detected this issue as fixed in range 525196:525217.

Detailed report: https://clusterfuzz.com/testcase?key=6741810952273920

Fuzzer: libFuzzer_swiftshader_vertex_routine_fuzzer
Job Type: libfuzzer_chrome_asan
Platform Id: linux

Crash Type: Heap-buffer-overflow READ 4
Crash Address: 0x6030000097a8
Crash State:
  ConstantUnion::operator-
  TIntermediate::addBinaryMath
  TParseContext::addBinaryMath
  
Sanitizer: address (ASAN)

Recommended Security Severity: Medium

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan&range=521502:521564
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_asan&range=525196:525217

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6741810952273920

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 6741810952273920 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