[Security] Bound Dots3 NOTE video audio decode duration and bytes

[jperezdealgaba]

Summary

The Dots3 NOTE video preprocessor decoded a request-supplied video's audio track with an unbounded get_all_samples() call, so a small container with a long audio stream could expand into gigabytes of PCM during multimodal preprocessing. This routes that path through the shared torchcodec audio loader, which already enforces the server duration and decoded-byte limits.

Changes

• vllm/models/dots3_note/common/video.py: decode video audio via load_audio_torchcodec with VLLM_MAX_AUDIO_DECODE_DURATION_S and VLLM_MAX_AUDIO_DECODE_BYTES. Duration and byte-limit errors fail the request; missing or corrupt audio tracks still skip audio.
• tests/models/dots3_note/test_video_audio_decode.py: unit coverage for forwarded limits, over-duration and over-bytes rejection, missing-audio skip, preprocess propagation, and audio_cap=0 not decoding.

Codepath coverage

• All HTTP and offline entry points that feed Dots3 NOTE video bytes (/v1/chat/completions, batch, /invocations, gRPC generate, LLM.generate) go through _decode_audio. That sink is now bounded.
• Direct input_audio / audio_url still use AudioMediaIO, which already passes the same limits.
• NanoNemotronVL video-audio extraction already passes the duration limit and is unchanged.
• use_audio_in_video in chat parsing fetches audio through MediaConnector / AudioMediaIO and is unchanged.

Duplicate-work check

Searched open, draft, and recently merged PRs for dots3_note, _decode_audio, get_all_samples, and load_audio_torchcodec. Hits such as #53610 (processor refactor), #51894 (channel-count guard on the shared loader), and #56056 (PyAV packed-frame conversion) do not bound this sink.

Tests

• test_decode_audio_forwards_duration_and_byte_limits
• test_decode_audio_rejects_over_duration
• test_decode_audio_rejects_over_decode_bytes
• test_decode_audio_skips_missing_audio_track
• test_preprocess_rejects_over_duration_audio
• test_preprocess_skips_audio_decode_when_audio_cap_is_zero

.venv/bin/python -m pytest tests/models/dots3_note/test_video_audio_decode.py -v

6 passed.

.venv/bin/pre-commit run --files vllm/models/dots3_note/common/video.py tests/models/dots3_note/test_video_audio_decode.py passed.

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