Support for LLVM 18 fuzzing

[Darksonn]

The Tokio build on oss-fuzz has started failing with the following output:

Running fuzz_linked_list
Running fuzz_stream_map
Traceback (most recent call last):
  File "/usr/local/bin/profraw_update.py", line 129, in <module>
    sys.exit(main())
  File "/usr/local/bin/profraw_update.py", line 120, in main
    profraw_latest = upgrade(profraw_base, sect_prf_cnts, sect_prf_data)
  File "/usr/local/bin/profraw_update.py", line 87, in upgrade
    relativize_address(data, offset + 16, dataref, sect_prf_cnts, sect_prf_data)
  File "/usr/local/bin/profraw_update.py", line 35, in relativize_address
    value = struct.unpack('Q', data[offset:offset + 8])[0]
struct.error: unpack requires a buffer of 8 bytes
warning: /workspace/out/libfuzzer-coverage-x86_64/dumps/fuzz_stream_map.16753151517152022731_0.profraw: unsupported instrumentation profile format version
error: no profile can be merged
[2024-02-21 06:24:21,463 INFO] Finding shared libraries for targets (if any).
[2024-02-21 06:24:21,473 INFO] Finished finding shared libraries for targets.
error: fuzz_stream_map: Failed to load coverage: No such file or directory
error: Could not load coverage information
error: No such file or directory: Could not read profile data!
Traceback (most recent call last):
  File "/usr/local/bin/profraw_update.py", line 129, in <module>
    sys.exit(main())
  File "/usr/local/bin/profraw_update.py", line 120, in main
    profraw_latest = upgrade(profraw_base, sect_prf_cnts, sect_prf_data)
  File "/usr/local/bin/profraw_update.py", line 87, in upgrade
    relativize_address(data, offset + 16, dataref, sect_prf_cnts, sect_prf_data)
  File "/usr/local/bin/profraw_update.py", line 35, in relativize_address
    value = struct.unpack('Q', data[offset:offset + 8])[0]
struct.error: unpack requires a buffer of 8 bytes
warning: /workspace/out/libfuzzer-coverage-x86_64/dumps/fuzz_linked_list.14910788477734546202_0.profraw: unsupported instrumentation profile format version
error: no profile can be merged

This error seems very similar to #6268, and the latest Rust release has the following in its changelog:

Update the minimum external LLVM to 16.

Let me know if the problem is on our end, or if there's anything I can do to help.

For more information, see the chromium bug for the build failure.

[djc]

Seeing this across all of the Rust projects I'm involved with:

• askama
• redis, cc @jaymell
• rustls, cc @ctz, @cpu
• trust-dns (should rename this to hickory-dns), cc @bluejekyll

[jrmuizel]

Also happening with qcms.

[seanmonstar]

Also with httparse.

[maflcko]

I presume one way to fix this would be with #8108 in the infra

[manunio]

Coverage builds are failing for the following Rust projects as well:

• toml_edit
• naga
• miniz_oxide
• ron
• bson-rust
• gimli

cc @oliverchang @jonathanmetzman @DonggeLiu

[jonathanmetzman]

OK, I will do a roll this week or next depending on when my latest clusterfuzz work ends

[Xuanwo]

There is another failure from apache/opendal#4242

[jonathanmetzman]

Sorry, I'm putting out some fires and will need to get back to this, later this week.

[oliverchang]

ryu also seems to be failing for a similar reason: https://oss-fuzz-build-logs.storage.googleapis.com/log-acc3b39e-2aa0-4769-a499-4c224201e35e.txt

[oliverchang]

@DavidKorczynski @AdamKorcz do you think this is something you'd be able to help with?

I believe @jonathanmetzman made a start on this, but was blocked on various projects being broken with the upgrade.

Alternatively, could we also pin Rust to an older version for now (https://github.com/google/oss-fuzz/blob/master/infra/base-images/base-builder/install_rust.sh)?

[maflcko]

I believe @jonathanmetzman made a start on this, but was blocked on various projects being broken with the upgrade.

If there are not too many projects affected, an alternative could be to temporarily pin them to the old docker image by hash.

[DavidKorczynski]

Proposed a fix here #11681 downgrading Rust which can be used until LLVM 18 upgrade lands.