From: Karel Zak <kzak@redhat.com>
Date: Wed, 27 May 2026 10:21:02 +0000 (+0200)
Subject: libmount: use fd_target in hook_idmap for move_mount()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8aa3af65b2b2a57bd40ecc47467d58d27cc9d3a7;p=thirdparty%2Futil-linux.git

libmount: use fd_target in hook_idmap for move_mount()

Use the pinned fd_target with MOVE_MOUNT_T_EMPTY_PATH for restricted
users instead of string-based move_mount().  Re-open the target fd
after mount to point to the mounted filesystem root.

Signed-off-by: Karel Zak <kzak@redhat.com>
---

diff --git a/libmount/src/hook_idmap.c b/libmount/src/hook_idmap.c
index b62079527..88c04e14c 100644
--- a/libmount/src/hook_idmap.c
+++ b/libmount/src/hook_idmap.c
@@ -352,10 +352,25 @@ static int hook_mount_post(
 
 	/* Attach the idmapped mount. */
 	if (is_private) {
+		unsigned int mmflags = MOVE_MOUNT_F_EMPTY_PATH;
+
 		/* Unmount the old, non-idmapped mount we just cloned and idmapped. */
 		umount2(target, MNT_DETACH);
 
-		rc = move_mount(fd_tree, "", -1, target, MOVE_MOUNT_F_EMPTY_PATH);
+		if (mnt_context_target_fd_required(cxt)) {
+			int fd_tgt = mnt_context_get_target_fd(cxt);
+
+			if (fd_tgt < 0) {
+				rc = -errno;
+				goto done;
+			}
+			mmflags |= MOVE_MOUNT_T_EMPTY_PATH;
+			rc = move_mount(fd_tree, "", fd_tgt, "", mmflags);
+		} else
+			rc = move_mount(fd_tree, "", AT_FDCWD, target, mmflags);
+
+		if (rc == 0)
+			rc = mnt_context_reopen_target_fd(cxt);
 		if (rc < 0) {
 			mnt_context_syscall_save_status(cxt, "move_mount", 0);
 			if (!mnt_context_read_mesgs(cxt, fd_tree)) {