fix AtLocation.chdir for the mixed case

When both fd and location are given, it would previously ignore the fd
component. To properly implement that, we must open and fchdir.

1 files changed, 7 insertions, 1 deletions

diff --git a/linuxnamespaces/atlocation.py b/linuxnamespaces/atlocation.py
index 20d402a..a4255a6 100644
--- a/linuxnamespaces/atlocation.py
+++ b/linuxnamespaces/atlocation.py
@@ -7,6 +7,7 @@ to work with a location described in this way and this module provides support
 code for doing so.
 """
 
+import contextlib
 import enum
 import errno
 import os
@@ -218,7 +219,12 @@ class AtLocation:
                 "chdir on AtLocation only supports flag AT_EMPTY_PATH"
             )
         assert self.location
-        return os.chdir(self.location)
+        if self.fd == AT_FDCWD:
+            return os.chdir(self.location)
+        with contextlib.closing(
+            FileDescriptor(self.open(flags=os.O_PATH | os.O_CLOEXEC))
+        ) as dirfd:
+            return os.fchdir(dirfd)
 
     def chmod(self, mode: int) -> None:
         """Wrapper for os.chmod or os.fchmod."""