kwiberg @ could you please look into this.please feel free to re-assigned back if needed. thanks in advance !
might be a suspected Changelist: https://chromium.googlesource.com/external/webrtc/trunk/webrtc.git/+/b9a5d2a304565d81be4a562deabd8397cc9a818a

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I thought this would be a simple case of replacing << x with * (1 << x), but the left shift that fails is this one:

    filtered_current_level_ = std::max(0,
        filtered_current_level_ -
        (time_stretched_samples << 8) / static_cast<int>(packet_len_samples));

I'm not 100% sure, but it looks like time_stretched_samples may be intended to never be negative, which would make this bug much more interesting than the typical "left shift of negative value" bug.

Reassigning to Dr. NetEq.

The following revision refers to this bug:
  https://webrtc.googlesource.com/src.git/+/8731176b922ad7d82d0407f2ac36d9f5396f9ac2

commit 8731176b922ad7d82d0407f2ac36d9f5396f9ac2
Author: Henrik Lundin <henrik.lundin@webrtc.org>
Date: Mon Oct 23 11:56:47 2017

NetEq: Fix an UBSan error

UBSan will trigger when shifting a negative value. This change avoids
that by replacing "x << 8" with "x * (1 << 8)".

Bug:  chromium:666877 
Change-Id: Ic89bd98e5a3feff35075df96b104b386cb4d8803
Reviewed-on: https://webrtc-review.googlesource.com/14552
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20387}
[modify] https://crrev.com/8731176b922ad7d82d0407f2ac36d9f5396f9ac2/modules/audio_coding/neteq/buffer_level_filter.cc

ClusterFuzz has detected this issue as fixed in range 510927:510949.

Detailed report: https://clusterfuzz.com/testcase?key=5641614816182272

Fuzzer: libFuzzer_neteq_rtp_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Undefined-shift
Crash Address: 
Crash State:
  webrtc::BufferLevelFilter::Update
  webrtc::DecisionLogic::FilterBufferLevel
  webrtc::DecisionLogic::GetDecision
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=423119:423133
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=510927:510949

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5641614816182272

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.

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.

(bulk edit)

ClusterFuzz testcase 5641614816182272 is verified as fixed, so closing issue as verified.

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