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Motivation

I didn't do things quite right in 496e43e:

  • Forgot to remove the now-redundant isAllowed check.

  • Called the non-virtual, not the superclass's impl, in addDependencyPrep, causing bad recursion / UB.

Doing this fixes a crash I encountered with manual testing an Nix Ninja --- hopefully we will get Nix Ninja or similar in a NixOS test longer term to defend against this thing happening again.

Context

496e43e


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I didn't do things quite right in 496e43e:

- Forgot to remove the now-redundant `isAllowed` check.

- Called the non-virtual, not the superclass's impl, in
  `addDependencyPrep`, causing bad recursion / UB.

Doing this fixes a crash I encountered with manual testing an Nix Ninja
--- hopefully we will get Nix Ninja or similar in a NixOS test longer
term to defend against this thing happening again.
@Ericson2314 Ericson2314 requested a review from xokdvium December 7, 2025 16:35
@xokdvium xokdvium added the backport 2.32-maintenance Automatically creates a PR against the branch label Dec 7, 2025
@Ericson2314 Ericson2314 enabled auto-merge December 7, 2025 17:13
@Ericson2314 Ericson2314 added this pull request to the merge queue Dec 7, 2025
Merged via the queue into master with commit d8ad000 Dec 7, 2025
21 checks passed
@Ericson2314 Ericson2314 deleted the fix-add-dep branch December 7, 2025 18:11
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Successfully created backport PR for 2.32-maintenance:

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Successfully created backport PR for 2.31-maintenance:

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Backport failed for 2.32-maintenance, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin 2.32-maintenance
git worktree add -d .worktree/backport-14729-to-2.32-maintenance origin/2.32-maintenance
cd .worktree/backport-14729-to-2.32-maintenance
git switch --create backport-14729-to-2.32-maintenance
git cherry-pick -x 4652345ac3ca3a804fe6176df8a429d518e58ee5

philiptaron added a commit to philiptaron/nixpkgs that referenced this pull request Jan 5, 2026
- **Fix heap-use-after-free crash under high build load** ([NixOS#14772](NixOS/nix#14772))

  Fixed a daemon segfault that could occur under high build load. The issue was caused by the `initialOutputs` field referencing data from an activation frame that had gone out of scope during coroutine tail-call optimization in the build scheduler.

- **Fix segfault when querying non-existent derivation files** ([NixOS#14571](NixOS/nix#14571), [NixOS#14572](NixOS/nix#14572))

  Running `nix derivation show /nix/store/...-doesnotexist.drv` would crash with a segfault. Now properly returns an "invalid store path" error.

- **Fix RestrictedStore::addDependency crash** ([NixOS#14729](NixOS/nix#14729))

  Fixed a crash caused by incorrect non-virtual interface pattern implementation that led to bad recursion/UB in `addDependencyPrep`.

- **Fix "dynamic attributes not allowed in let" regression** ([NixOS#14642](NixOS/nix#14642), [NixOS#14646](NixOS/nix#14646))

  Expressions like `let a = 1; "b" = 2; ${"c"} = 3; in [ a b c ]` that worked in 2.30 would incorrectly fail in 2.32.x. This was caused by the ExprString arena optimization, which has been reverted.

- **Fix fetchGit with `ref = "HEAD"` regression** ([NixOS#13948](NixOS/nix#13948), [NixOS#14672](NixOS/nix#14672))

  `fetchGit { url = "..."; ref = "HEAD"; }` was broken and returned "revspec 'HEAD' not found".

- **Fix unnecessary substituter queries** ([NixOS#14836](NixOS/nix#14836), [NixOS#14837](NixOS/nix#14837))

  Fixed a regression where Nix would query all substituters (including `cache.nixos.org`) even when a higher-priority local substituter already had the path. This caused unnecessary network traffic.

- **Fix curl with c-ares failing DNS resolution in macOS sandbox** ([NixOS#14792](NixOS/nix#14792))

  When curl is built with c-ares (as in recent nixpkgs), DNS resolution would fail inside the Nix build sandbox on macOS with "Could not contact DNS servers".

- **Fix file system race conditions in store optimization** ([NixOS#14676](NixOS/nix#14676), [NixOS#7273](NixOS/nix#7273))

  Multiple fixes to `optimizePath_`:
  - Actually call `remove()` when `rename()` fails
  - Propagate error codes in `createSymlink()`
  - Make `AutoDelete` non-copyable and non-movable to prevent use-after-free

- **Include path in world-writable error messages** ([NixOS#14785](NixOS/nix#14785))

  The error message for world-writable directory checks now includes the specific path that failed, making debugging easier.

- **Documentation: correct `build-dir` error information** ([NixOS#14745](NixOS/nix#14745))

  Fixed out-of-date information in the manual about `build-dir` errors and added links to relevant settings.

- CI improvements: added `upload-release.yml` workflow, improved Docker push workflow configurability, updated magic-nix-cache with post-build-hook fix
- Documented maintainer git tag signing process
- Fixed lowdown override compatibility with newer nixpkgs
- Removed mdbook-linkcheck and added support for mdbook 0.5.x
- Remove static data from headers to fix compilation issues

---

Diff: NixOS/nix@2.32.4...2.32.5
philiptaron added a commit to philiptaron/nixpkgs that referenced this pull request Jan 5, 2026
# Changelog: Nix 2.32.5

## Bug Fixes

### Critical Crashes Fixed

- **Fix heap-use-after-free crash under high build load** ([NixOS#14772](NixOS/nix#14772))

  Fixed a daemon segfault that could occur under high build load. The issue was caused by the `initialOutputs` field referencing data from an activation frame that had gone out of scope during coroutine tail-call optimization in the build scheduler.

- **Fix segfault when querying non-existent derivation files** ([NixOS#14571](NixOS/nix#14571), [NixOS#14572](NixOS/nix#14572))

  Running `nix derivation show /nix/store/...-doesnotexist.drv` would crash with a segfault. Now properly returns an "invalid store path" error.

- **Fix RestrictedStore::addDependency crash** ([NixOS#14729](NixOS/nix#14729))

  Fixed a crash caused by incorrect non-virtual interface pattern implementation that led to bad recursion/UB in `addDependencyPrep`.

### Regressions Fixed

- **Fix "dynamic attributes not allowed in let" regression** ([NixOS#14642](NixOS/nix#14642), [NixOS#14646](NixOS/nix#14646))

  Expressions like `let a = 1; "b" = 2; ${"c"} = 3; in [ a b c ]` that worked in 2.30 would incorrectly fail in 2.32.x. This was caused by the ExprString arena optimization, which has been reverted.

- **Fix fetchGit with `ref = "HEAD"` regression** ([NixOS#13948](NixOS/nix#13948), [NixOS#14672](NixOS/nix#14672))

  `fetchGit { url = "..."; ref = "HEAD"; }` was broken and returned "revspec 'HEAD' not found".

- **Fix unnecessary substituter queries** ([NixOS#14836](NixOS/nix#14836), [NixOS#14837](NixOS/nix#14837))

  Fixed a regression where Nix would query all substituters (including `cache.nixos.org`) even when a higher-priority local substituter already had the path. This caused unnecessary network traffic.

### Platform-Specific Fixes

- **Fix curl with c-ares failing DNS resolution in macOS sandbox** ([NixOS#14792](NixOS/nix#14792))

  When curl is built with c-ares (as in recent nixpkgs), DNS resolution would fail inside the Nix build sandbox on macOS with "Could not contact DNS servers".

### Store & File System Fixes

- **Fix file system race conditions in store optimization** ([NixOS#14676](NixOS/nix#14676), [NixOS#7273](NixOS/nix#7273))

  Multiple fixes to `optimizePath_`:
  - Actually call `remove()` when `rename()` fails
  - Propagate error codes in `createSymlink()`
  - Make `AutoDelete` non-copyable and non-movable to prevent use-after-free

## Improvements

- **Include path in world-writable error messages** ([NixOS#14785](NixOS/nix#14785))

  The error message for world-writable directory checks now includes the specific path that failed, making debugging easier.

- **Documentation: correct `build-dir` error information** ([NixOS#14745](NixOS/nix#14745))

  Fixed out-of-date information in the manual about `build-dir` errors and added links to relevant settings.

## Maintenance

- CI improvements: added `upload-release.yml` workflow, improved Docker push workflow configurability, updated magic-nix-cache with post-build-hook fix
- Documented maintainer git tag signing process
- Fixed lowdown override compatibility with newer nixpkgs
- Removed mdbook-linkcheck and added support for mdbook 0.5.x
- Remove static data from headers to fix compilation issues
- **Fix heap-use-after-free crash under high build load** ([NixOS#14772](NixOS/nix#14772))

---

Diff: NixOS/nix@2.32.4...2.32.5
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