From 10b9c1b2b269b96dcb8b3d298491fa143d1663e8 Mon Sep 17 00:00:00 2001
From: Cole Helbling <cole.e.helbling@outlook.com>
Date: Mon, 4 Apr 2022 10:16:30 -0700
Subject: [PATCH] libutil: save cwd fd in restoreMountNamespace
MIME-Version: 1.0
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This doesn't work very well (maybe I'm misunderstanding the desired
implementation):

    : ~/w/vc/nix ; doas outputs/out/bin/nix --experimental-features 'nix-command flakes' develop -c pwd
    pwd: couldn't find directory entry in ‘../../../..’ with matching i-node
---
 src/libutil/util.cc | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 1f800f3f4..701545589 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1690,7 +1690,6 @@ void setStackSize(size_t stackSize)
 
 #if __linux__
 static AutoCloseFD fdSavedMountNamespace;
-static AutoCloseFD fdSavedCwd;
 #endif
 
 void saveMountNamespace()
@@ -1702,11 +1701,6 @@ void saveMountNamespace()
         if (!fd)
             throw SysError("saving parent mount namespace");
         fdSavedMountNamespace = std::move(fd);
-
-        fd = open("/proc/self/cwd", O_RDONLY);
-        if (!fd)
-            throw SysError("saving cwd");
-        fdSavedCwd = std::move(fd);
     });
 #endif
 }
@@ -1715,6 +1709,10 @@ void restoreMountNamespace()
 {
 #if __linux__
     try {
+        AutoCloseFD fdSavedCwd = open("/proc/self/cwd", O_RDONLY);
+        if (!fdSavedCwd) {
+            throw SysError("saving cwd");
+        }
         if (fdSavedMountNamespace && setns(fdSavedMountNamespace.get(), CLONE_NEWNS) == -1)
             throw SysError("restoring parent mount namespace");
         if (fdSavedCwd && fchdir(fdSavedCwd.get()) == -1) {