From 3604e3ae9d333cd7d468a8be4b277adfd9427f1b Mon Sep 17 00:00:00 2001
From: Maximilian Bosch <maximilian@mbosch.me>
Date: Tue, 30 Dec 2025 15:45:33 +0100
Subject: [PATCH] nixos/doc/release-notes: document glibc execstack change

---
 .../manual/release-notes/rl-2605.section.md   | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/nixos/doc/manual/release-notes/rl-2605.section.md b/nixos/doc/manual/release-notes/rl-2605.section.md
index 9d4f926dc718..d382e528525e 100644
--- a/nixos/doc/manual/release-notes/rl-2605.section.md
+++ b/nixos/doc/manual/release-notes/rl-2605.section.md
@@ -90,3 +90,41 @@ of pulling the upstream container image from Docker Hub. If you want the old beh
 - `services.openssh` now supports generating host SSH keys by setting `services.openssh.generateHostKeys = true` while leaving `services.openssh.enable` disabled.  This is particularly useful for systems that have no need of an SSH daemon but want SSH host keys for other purposes such as using agenix or sops-nix.
 
 - `services.slurm` now supports slurmrestd usage through the `services.slurm.rest` NixOS options.
+
+- `glibc` has been updated to version 2.42.
+
+  This version no longer makes the stack executable when a shared library requires this. A symptom
+  is an error like
+
+  > cannot enable executable stack as shared object requires: Invalid argument
+
+  This is usually a bug. Please consider reporting it to the software maintainers.
+
+  In a lot of cases, the library requires the execstack by mistake only. The following workarounds exist:
+
+  * When building the shared library in question from source, use the following linker flags to force turning off the
+    executable flag:
+
+    ```nix
+    mkDerivation {
+      # …
+
+      env.NIX_LDFLAGS = "-z,noexecstack";
+    }
+    ```
+
+  * If the sources are not available, the execstack-flag can be cleared with `patchelf`:
+
+    ```
+    patchelf --clear-execstack binary-only.so
+    ```
+
+  * If the shared library to be loaded actually requires an executable stack and it isn't turned
+    on by the application loading it, you may force allowing that behavior by setting the
+    following environment variable:
+
+    ```
+    GLIBC_TUNABLES=glibc.rtld.execstack=2
+    ```
+
+    **Do not set this globally!** This makes your setup inherently less secure.