Unable to find the suspect, hence cc'ing mmoroz@ for further investigation and more inputs on this.

Interesting. I can reproduce it locally:

$ ASAN_OPTIONS=detect_leaks=1 ~/Projects/new/chromium/src/out/Release/net_data_job_fuzzer ./9857977d541b1065f209647df215be4e5a9c1a47 
INFO: Seed: 1988803739
/out/Release/net_data_job_fuzzer: Running 1 inputs 1 time(s) each.
./9857977d541b1065f209647df215be4e5a9c1a47 ... 545 ms

=================================================================
==47259==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 72 byte(s) in 1 object(s) allocated from:
    #0 0x4bfaa4  (<...>/out/Release/net_data_job_fuzzer+0x4bfaa4)
    #1 0x7ffa5d3898b3  (/usr/lib/x86_64-linux-gnu/libnss3.so+0x718b3)

Direct leak of 72 byte(s) in 1 object(s) allocated from:
    #0 0x4bfaa4  (<...>/out/Release/net_data_job_fuzzer+0x4bfaa4)
    #1 0x7ff8caea2373  (/usr/lib/x86_64-linux-gnu/nss/libnssckbi.so+0x30373)

SUMMARY: AddressSanitizer: 144 byte(s) leaked in 2 allocation(s).

Assigning to csharrison@, as an author of the fuzzer.

Chrome is using a system version of libnss, this is why FindIt cannot find any commits.

What's the proper way to symbolize reports from libfuzzer? I'm also able to repro this locally. 

cc mmenke as FYI.

$ export ASAN_OPTIONS=symbolize=1

Should enable symbolization, but in this particular case we need to have a libnss built with symbols. The system version is stripped.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=6175018098884608

Fuzzer: net_host_resolver_impl_fuzzer
Job Type: libfuzzer_chrome_asan
Platform Id: linux

Crash Type: Direct-leak
Crash Address: 
Crash State:
  libnss3.so
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=libfuzzer_chrome_asan&range=397426:397565
Fixed: https://cluster-fuzz.appspot.com/revisions?job=libfuzzer_chrome_asan&range=405519:405688

Minimized Testcase (0.12 Kb): https://cluster-fuzz.appspot.com/download/AMIfv97k7atIhamkdoJb3JkWinY2NlliozA6frDWbNi7v8Laq9FXeRUXwM1YpSk9kxjkJKX35hRVkohJSFkznwdczrqZE_fJg6JAa7Y5jnGhXqxcePo7j_OlYZTkJuBTKp0mGBL5qnWH5PGBVW0H64AJ3SDO7s8d0w?testcase_id=6175018098884608

Filer: ajha

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

Removing EditIssue view restrictions from ClusterFuzz filed bugs. If you believe that this issue should still be restricted, please reapply the label.

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

Can no longer reproduce on TOT, going to re-spin the report.

ClusterFuzz has detected this issue as fixed in range 425682:425723.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=4953786170998784

Fuzzer: net_data_job_fuzzer
Job Type: libfuzzer_chrome_asan
Platform Id: linux

Crash Type: Direct-leak
Crash Address: 
Crash State:
  libnss3.so
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=libfuzzer_chrome_asan&range=395675:395769
Fixed: https://cluster-fuzz.appspot.com/revisions?job=libfuzzer_chrome_asan&range=425682:425723

Minimized Testcase (0.04 Kb): https://cluster-fuzz.appspot.com/download/AMIfv97bONwdJNHX5HRF6uR5Jwds6ryfVQW0Xq17M_Z7jr8y4hwNQDHs3G4X_LNCKYqRugESvnKJrq8OE2ViPaYKHYJLWuhu7bZNbrqLg1-bCCou753SJNM_ldcQPBpCkFsN2dXOjf9VGu6_Cwr8U_WgSlUAFfikKA?testcase_id=4953786170998784

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.

This bug is confusing but since it no longer repros and is "fixed" according to clusterfuzz there isn't much we can do. WontFixing.