Netdata fixes part 33

[stelfrag]

Summary

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

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Summary by cubic

Hardens the circular buffer to prevent infinite growth loops, integer overflow, and out-of-range write positions, with no change for valid callers.

• Bug Fixes
  • Growth: seed zero-size buffers at 1 byte and cap before doubling to avoid stuck loops and overflow.
  • Capacity checks: reject impossible add/reserve requests upfront; use subtraction-based bounds (no wrapped d_len + len or write + size).
  • Commit safety: validate inputs, ensure commit fits the remaining ring capacity, and update the write index with wrap-safe arithmetic; ignore overlarge/invalid commits.

^{Written for commit 0a4f672. 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 1 file

Confidence score: 5/5

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

Architecture diagram

sequenceDiagram
    participant Client as Caller Component
    participant CB as Circular Buffer
    participant Alloc as Memory Allocator

    Client->>CB: cbuffer_add_unsafe(buf, d, d_len)

    CB->>CB: Compute used size len
    alt impossible: len ≥ max_size or d_len > max_size - len
        CB-->>Client: return 1 (error, no change)
    else possible
        loop while space insufficient (len ≥ size or d_len ≥ size - len)
            CB->>CB: cbuffer_realloc_unsafe(buf)
            alt growth succeeds
                CB->>Alloc: realloc (new_size = max_size or capped doubling, seed 1 if size 0)
                Alloc-->>CB: new buffer
                CB->>CB: move data, update size
            else growth fails
                CB-->>Client: return 1
            end
        end
        alt d_len < size - write
            CB->>CB: memcpy contiguous write
            CB->>CB: write += d_len
        else
            CB->>CB: memcpy wrap‑aware (two parts)
            CB->>CB: write updated with wrap
        end
        CB-->>Client: return 0
    end
    Note over Client,CB: Similar guards apply to cbuffer_reserve_unsafe and cbuffer_commit_reserved_unsafe (validation, safe wrap arithmetic)

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_{Re-trigger cubic}

[Copilot]

Pull request overview

Hardens libnetdata’s adaptive circular buffer to avoid infinite growth loops, integer overflow during resizing, and out-of-range write/commit arithmetic, while preserving behavior for valid callers.

Changes:

• Make buffer growth overflow-safe and able to recover from a zero-sized buffer by seeding growth at 1 byte and capping before doubling.
• Replace addition-based capacity checks (len + size) with subtraction-based bounds checks to avoid wraparound and impossible requests.
• Make reserve/add/commit pointer arithmetic wrap-safe and add defensive validation in cbuffer_commit_reserved_unsafe().

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[thiagoftsm]

No issues found during runtime. LGTM!