Netdata fixes part 19

[stelfrag]

Summary

• Netdata fixes based on fix: harden netdata memory safety edges #22881

---

Summary by cubic

Hardened flag handling, URL decoding, and query tail-fill to remove undefined behavior and data races without changing behavior. Improves safety in multi-threaded paths and malformed input handling.

• Bug Fixes
  • Read and snapshot rrdcontext/instance/metric flags atomically; use rrd_flags_get()/rrd_flag_is_collected() in triggers, queues, and API v2; queue stores queued_flags from atomic snapshots.
  • Seed compare-exchange helpers with __atomic_load_n to avoid racy plain loads.
  • URL percent-decoding: use unsigned bytes with ctype and bit shifts; fix UTF‑8 byte-length counting to shift an unsigned copy.
  • Queries: add a guarded rrdr_line_next() and use it for tail-fill to keep bounds checks consistent.
  • OS cpuset parsing: make the scratch buffer thread-local to prevent cross‑thread races.

^{Written for commit cc0b3e1. Summary will update on new commits.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[cubic-dev-ai]

No issues found across 9 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Architecture diagram

sequenceDiagram
    participant API as API v2
    participant RC as RRDCONTEXT
    participant RI as RRDINSTANCE
    participant RM as RRDMETRIC
    participant PPQueue as PP Queue
    participant Query as Query Engine
    participant URL as URL Decoder
    participant CPU as CPUset Parser

    Note over API,CPU: Key runtime components for flag safety, URL decoding, query bounds, and thread safety

    par API v2 Context Flow
        API->>RC: rrdcontext_to_json_v2_add_context()
        RC->>RC: rrd_flags_get(rc) - atomic snapshot
        RC-->>API: context flags

        API->>RI: iterate rrdinstances
        RI->>RI: rrd_flag_is_collected(ri) - atomic read
        alt window enabled
            RI->>RI: query_matches_retention() with atomic flag
        end

        RI->>RM: iterate rrdmetrics
        RM->>RM: rrd_flag_is_collected(rm) - atomic read
        alt window enabled
            RM->>RM: query_matches_retention() with atomic flag
        end
    end

    par Trigger Updates Flow
        Note over RC,Query: Update triggers queue context for post-processing
        RC->>RC: rrdcontext_trigger_updates()
        RC->>RC: rrd_flags_get(rc) - atomic snapshot
        RC->>PPQueue: rrdcontext_queue_for_post_processing(flags snapshot)

        Note over RI: Instance triggers
        RI->>RI: rrdinstance_trigger_updates()
        RI->>RI: rrd_flags_get(ri) - atomic snapshot
        RI->>PPQueue: rrdcontext_queue_for_post_processing(flags snapshot)

        Note over RM: Metric triggers
        RM->>RM: rrdmetric_trigger_updates()
        RM->>RM: rrd_flags_get(rm) - atomic snapshot
        RM->>PPQueue: rrdcontext_queue_for_post_processing(flags snapshot)

        Note over PPQueue: Queue stores queued_flags from atomic snapshot
        PPQueue->>PPQueue: rrdcontext_add_to_pp_queue()
        PPQueue->>PPQueue: rc->pp.queued_flags = rrd_flags_get(rc)
        alt already queued
            PPQueue->>PPQueue: queued_flags |= rrd_flags_get(rc)
        end
    end

    par Query Execution Flow
        Query->>Query: rrd2rrdr_query_execute()
        Query->>Query: points_added loop
        loop fill tail with empty values
            Query->>Query: rrdr_line_next(r, rrdr_line)
            Note over Query: Guarded increment with bounds check
            Query->>Query: set RRDR_VALUE_EMPTY
        end
        alt final fill
            Query->>Query: rrdr_line = rrdr_line_next(r, rrdr_line)
            Query->>Query: same safe increment
        end
    end

    par URL Decoding Flow
        URL->>URL: url_percent_escape_decode()
        URL->>URL: from_hex() with uint8_t cast
        Note over URL: Unsigned byte operations for hex conversion

        URL->>URL: url_utf8_get_byte_length()
        URL->>URL: uint8_t byte = (uint8_t)c
        Note over URL: Right-shift on unsigned copy for UTF-8 length
    end

    par CPUset Parsing Flow
        Note over CPU: Thread-local buffers prevent cross-thread races
        CPU->>CPU: os_read_cpuset_cpus()
        CPU->>CPU: static __thread char *buf
        CPU->>CPU: static __thread size_t buf_size
    end

    Note over API,CPU: Atomic operations use __atomic_load_n for compare-exchange helpers
    Note over RC,PPQueue: rrd_flag_add_remove_atomic/rrd_flags_replace_atomic seed with atomic load

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_{Re-trigger cubic}

[thiagoftsm]

PR is working as expected, LGTM!