Predator and CL did not provide any possible suspects.
Using Code Search for the file, "FlatTreeTraversal.cpp" assigning to the concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/5e53c60ebe374282c8c2864a8e6d1d864afa221a

@rune -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

Does not seem to be related to my changes.

I can reproduce this stack trace in content_shell with a mouse-down + left dragging after load. There are DCHECKs triggering in the editing code before reaching the crash, though.

The crash happens because

CanBeAnchorNode<blink::EditingAlgorithm<blink::FlatTreeTraversal>()

is called with a null anchor_node which is passed in the FlatTreeTraversal which expects a non-null node. The code starts with a TEXTAREA without a parent node. ComputeContainerNode() returns null because of that.

Lower to Pri-3, since this is caused by unusual HTML markup.

ClusterFuzz has detected this issue as fixed in range 489161:489186.

Detailed report: https://clusterfuzz.com/testcase?key=6265656235524096

Fuzzer: inferno_layout_test_unmodified
Job Type: windows_asan_chrome_no_sandbox
Platform Id: windows

Crash Type: Null-dereference READ
Crash Address: 0x00000008
Crash State:
  blink::FlatTreeTraversal::TraverseChild
  blink::FlatTreeTraversal::ChildAt
  blink::PositionIteratorAlgorithm<class blink::EditingAlgorithm<class blink::Flat
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=windows_asan_chrome_no_sandbox&range=456190:456233
Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome_no_sandbox&range=489161:489186

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6265656235524096


Additional requirements: Requires Gestures

See https://github.com/google/clusterfuzz-tools 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 6265656235524096 is verified as fixed, so closing issue as verified.

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