[PR #43] [MERGED] fix(overlaybd): reject truncated mapped reads #135

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opened 2026-10-29 14:20:04 +00:00 by bsakaguchi · 0 comments

bsakaguchi commented

2026-10-29 14:20:04 +00:00

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📋 Pull Request Information

Original PR: https://github.com/kvcache-ai/AgentENV/pull/43
Author: @morluto
Created: 7/28/2026
Status: ✅ Merged
Merged: 7/30/2026
Merged by: @huajq

Base: main ← Head: fix/overlaybd-truncated-mapped-reads

📝 Commits (2)

def3fbc fix(overlaybd): reject truncated mapped reads
c8c5317 fix(overlaybd): verify short-read retry offsets

📊 Changes

3 files changed (+91 additions, -36 deletions)

View changed files

📝 storage/overlaybd/src/lsmt/file/readonly.rs (+8 -11)
📝 storage/overlaybd/src/lsmt/file/readwrite.rs (+10 -11)
📝 storage/overlaybd/src/lsmt/file/tests.rs (+73 -14)

📄 Description

Problem

Mapped LSMT reads currently zero-fill the remainder of the destination buffer when a backing layer returns fewer bytes than requested. A truncated mapped extent can therefore be returned as apparently valid filesystem or VM-memory data.

Explicit holes and zero mappings are handled separately and should continue to produce zeros.

mapping lookup
  +-- hole / zero mapping ------------> fill with zeros
  |
  `-- mapped extent
          |
          v
      read remaining bytes <----------+
          |                           |
          +-- bytes, range incomplete +
          +-- range complete --------> return data
          `-- early EOF -------------> return error

Changes

Use the existing exact-read helper for mapped physical reads in both readonly and readwrite LSMT files.
Retry legal partial reads until the requested mapped range is filled.
Return unexpected EOF when the backing extent ends early.
Preserve zero-filling for explicit holes and zero mappings.

Validation

Added regression coverage for legal short-read retries and premature EOF in both readonly and writable LSMT stacks.
Against the previous implementation, the retry test observed a zero-filled tail and the truncation test incorrectly succeeded.
cargo test -p overlaybd --lib — 303 passed, 1 ignored.
cargo clippy -p overlaybd --all-targets -- -D warnings
cargo fmt --all

Closes #40.

_{🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.}

## 📋 Pull Request Information **Original PR:** https://github.com/kvcache-ai/AgentENV/pull/43 **Author:** [@morluto](https://github.com/morluto) **Created:** 7/28/2026 **Status:** ✅ Merged **Merged:** 7/30/2026 **Merged by:** [@huajq](https://github.com/huajq) **Base:** `main` ← **Head:** `fix/overlaybd-truncated-mapped-reads` --- ### 📝 Commits (2) - [`def3fbc`](https://github.com/kvcache-ai/AgentENV/commit/def3fbc72057b08b3e630fb597195c6ec9329465) fix(overlaybd): reject truncated mapped reads - [`c8c5317`](https://github.com/kvcache-ai/AgentENV/commit/c8c53170f3e04678e0732b391c897d083ed66242) fix(overlaybd): verify short-read retry offsets ### 📊 Changes **3 files changed** (+91 additions, -36 deletions) <details> <summary>View changed files</summary> 📝 `storage/overlaybd/src/lsmt/file/readonly.rs` (+8 -11) 📝 `storage/overlaybd/src/lsmt/file/readwrite.rs` (+10 -11) 📝 `storage/overlaybd/src/lsmt/file/tests.rs` (+73 -14) </details> ### 📄 Description ## Problem Mapped LSMT reads currently zero-fill the remainder of the destination buffer when a backing layer returns fewer bytes than requested. A truncated mapped extent can therefore be returned as apparently valid filesystem or VM-memory data. Explicit holes and zero mappings are handled separately and should continue to produce zeros. ```text mapping lookup +-- hole / zero mapping ------------> fill with zeros | `-- mapped extent | v read remaining bytes <----------+ | | +-- bytes, range incomplete + +-- range complete --------> return data `-- early EOF -------------> return error ``` ## Changes - Use the existing exact-read helper for mapped physical reads in both readonly and readwrite LSMT files. - Retry legal partial reads until the requested mapped range is filled. - Return `unexpected EOF` when the backing extent ends early. - Preserve zero-filling for explicit holes and zero mappings. ## Validation - Added regression coverage for legal short-read retries and premature EOF in both readonly and writable LSMT stacks. - Against the previous implementation, the retry test observed a zero-filled tail and the truncation test incorrectly succeeded. - `cargo test -p overlaybd --lib` — 303 passed, 1 ignored. - `cargo clippy -p overlaybd --all-targets -- -D warnings` - `cargo fmt --all` Closes #40. --- <sub>🔄 This issue represents a GitHub Pull Request. It cannot be merged through Gitea due to API limitations.</sub>

bsakaguchi

2026-10-29 14:20:04 +00:00