From d3dc64b81138417290ac31f6fb9171d3778f1ad3 Mon Sep 17 00:00:00 2001
From: Cole Helbling <cole.helbling@determinate.systems>
Date: Tue, 15 Jul 2025 09:56:07 -0700
Subject: [PATCH] external-derivation-builder: chdir into tmpdir

---
 src/libstore/unix/build/external-derivation-builder.cc | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/libstore/unix/build/external-derivation-builder.cc b/src/libstore/unix/build/external-derivation-builder.cc
index 79ce0ba45..a393d75d9 100644
--- a/src/libstore/unix/build/external-derivation-builder.cc
+++ b/src/libstore/unix/build/external-derivation-builder.cc
@@ -106,6 +106,9 @@ struct ExternalDerivationBuilder : DerivationBuilderImpl
 
                 args.insert(args.end(), jsonFile);
 
+                if (chdir(tmpDir.c_str()) == -1)
+                    throw SysError("changing into '%1%'", tmpDir);
+
                 chownToBuilder(topTmpDir);
 
                 setUser();