Add OSS-Fuzz integration for openxla/xla

[ricaskew]

Add OSS-Fuzz integration for openxla/xla

This PR registers openxla/xla with OSS-Fuzz, adding continuous fuzzing
coverage for XLA's HLO text-format parser and proto deserialization path.
This is the first OSS-Fuzz integration for openxla/xla.

Companion PR in openxla/xla adding the harness sources:
openxla/xla#42055

Note: this integration depends on the companion PR above. The build.sh
guard will exit non-zero until openxla/xla#42055 merges and
xla/fuzz/BUILD is present in the upstream tree. Exact error message:
ERROR: xla/fuzz/BUILD missing — PR-A (upstream harness landing) must merge before this OSS-Fuzz integration builds cleanly.
The OSS-Fuzz CI build will serve as the first end-to-end validation
in the clean pipeline environment.

Project details

homepage: https://openxla.org/xla
language: C++
sanitizers: address
fuzzing_engines: libfuzzer
primary_contact: xla-team@google.com

Harnesses

hlo_parser_fuzz — exercises xla::ParseAndReturnUnverifiedModule
against arbitrary text input bytes. Targets the HLO text-format parser
surface.

hlo_proto_fuzz — exercises xla::HloModule::CreateFromProto against
arbitrary byte sequences. Includes an explicit size guard against integer
overflow on the ParseFromArray size argument.

Build notes

XLA uses a hermetic LLVM18 toolchain that dynamic-links libc++. The
base-runner image does not ship libc++, so build.sh resolves this by
embedding --linkopt=-Wl,-rpath,$ORIGIN and staging the required libc++
shared objects alongside the fuzzer binaries in $OUT/.

The Dockerfile uses base-builder:ubuntu-24-04 and installs OpenJDK 17
via install_java.sh (matching the pattern used by other Google ML
projects in OSS-Fuzz). Bazel is installed via Bazelisk v1.20.0, which
respects XLA's pinned .bazelversion file.

Testing

Both harnesses were smoke-tested inside the OSS-Fuzz Docker base image:

• hlo_parser_fuzz: 100 runs, zero crashes, 2,371 coverage PCs with
  growth into xla::HloLexer and related parser code paths
• hlo_proto_fuzz: 100 runs, zero crashes, 819 coverage PCs with
  growth into xla::HloModuleConfig and protobuf TcParser family

[github-actions]

ricaskew is integrating a new project:
- Main repo: https://github.com/openxla/xla
- Criticality score: 0.64815

[ricaskew]

Companion harness PR in openxla/xla: openxla/xla#42055

[DavidKorczynski]

waiting for openxla/xla#42055 to be resolved