From 7fee08e53f5146b7ef8a48759c930ab29f8efc4e Mon Sep 17 00:00:00 2001
From: Anders Roxell <anders.roxell@linaro.org>
Date: Fri, 16 Jan 2026 10:17:05 +0100
Subject: [PATCH] tar_in: add keepdirlink option for --keep-directory-symlink

Add a new optional boolean argument 'keepdirlink' to tar_in that passes
--keep-directory-symlink to tar. This preserves existing symlinks to
directories when extracting, which is important for usrmerge systems
where /lib is a symlink to /usr/lib.

Without this option, extracting a tarball containing lib/modules/...
to / would replace the /lib symlink with a real directory, breaking
the system.

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
 daemon/tar.c              | 12 ++++++++----
 generator/actions_core.ml | 14 ++++++++++----
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/daemon/tar.c b/daemon/tar.c
index 1d6a4b7eb..063e41ba3 100644
--- a/daemon/tar.c
+++ b/daemon/tar.c
@@ -134,7 +134,7 @@ write_cb (void *fd_ptr, const void *buf, size_t len)
 /* Has one FileIn parameter. */
 /* Takes optional arguments, consult optargs_bitmask. */
 int
-do_tar_in (const char *dir, const char *compress, int xattrs, int selinux, int acls)
+do_tar_in (const char *dir, const char *compress, int xattrs, int selinux, int acls, int keepdirlink)
 {
   const char *filter;
   int err, r;
@@ -179,6 +179,9 @@ do_tar_in (const char *dir, const char *compress, int xattrs, int selinux, int a
   if (!(optargs_bitmask & GUESTFS_TAR_IN_ACLS_BITMASK))
     acls = 0;
 
+  if (!(optargs_bitmask & GUESTFS_TAR_IN_KEEPDIRLINK_BITMASK))
+    keepdirlink = 0;
+
   fd = mkstemp (error_file);
   if (fd == -1) {
     err = errno;
@@ -203,7 +206,7 @@ do_tar_in (const char *dir, const char *compress, int xattrs, int selinux, int a
   }
   fprintf (fp, "tar -C ");
   sysroot_shell_quote (dir, fp);
-  fprintf (fp, "%s -xf - %s%s%s%s2> %s",
+  fprintf (fp, "%s -xf - %s%s%s%s%s2> %s",
            filter,
            chown_supported ? "" : "--no-same-owner ",
            /* --xattrs-include=* is a workaround for a bug
@@ -213,6 +216,7 @@ do_tar_in (const char *dir, const char *compress, int xattrs, int selinux, int a
            xattrs ? "--xattrs --xattrs-include='*' " : "",
            selinux ? "--selinux " : "",
            acls ? "--acls " : "",
+           keepdirlink ? "--keep-directory-symlink " : "",
            error_file);
   if (fclose (fp) == EOF)
     goto cmd_error;
@@ -272,7 +276,7 @@ int
 do_tgz_in (const char *dir)
 {
   optargs_bitmask = GUESTFS_TAR_IN_COMPRESS_BITMASK;
-  return do_tar_in (dir, "gzip", 0, 0, 0);
+  return do_tar_in (dir, "gzip", 0, 0, 0, 0);
 }
 
 /* Has one FileIn parameter. */
@@ -280,7 +284,7 @@ int
 do_txz_in (const char *dir)
 {
   optargs_bitmask = GUESTFS_TAR_IN_COMPRESS_BITMASK;
-  return do_tar_in (dir, "xz", 0, 0, 0);
+  return do_tar_in (dir, "xz", 0, 0, 0, 0);
 }
 
 /* Has one FileOut parameter. */
diff --git a/generator/actions_core.ml b/generator/actions_core.ml
index b4ec6db87..96cf63135 100644
--- a/generator/actions_core.ml
+++ b/generator/actions_core.ml
@@ -2631,21 +2631,21 @@ To get the checksums for many files, use C<guestfs_checksums_out>.|} };
 
   { defaults with
     name = "tar_in"; added = (1, 0, 3);
-    style = RErr, [String (FileIn, "tarfile"); String (Pathname, "directory")], [OString "compress"; OBool "xattrs"; OBool "selinux"; OBool "acls"];
+    style = RErr, [String (FileIn, "tarfile"); String (Pathname, "directory")], [OString "compress"; OBool "xattrs"; OBool "selinux"; OBool "acls"; OBool "keepdirlink"];
     once_had_no_optargs = true;
     cancellable = true;
     tests = [
       InitScratchFS, Always, TestResultString (
         [["mkdir"; "/tar_in"];
-         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar"; "/tar_in"; "NOARG"; ""; ""; ""];
+         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar"; "/tar_in"; "NOARG"; ""; ""; ""; ""];
          ["cat"; "/tar_in/hello"]], "hello\n"), [];
       InitScratchFS, Always, TestResultString (
         [["mkdir"; "/tar_in_gz"];
-         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar.gz"; "/tar_in_gz"; "gzip"; ""; ""; ""];
+         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar.gz"; "/tar_in_gz"; "gzip"; ""; ""; ""; ""];
          ["cat"; "/tar_in_gz/hello"]], "hello\n"), [];
       InitScratchFS, IfAvailable "xz", TestResultString (
         [["mkdir"; "/tar_in_xz"];
-         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar.xz"; "/tar_in_xz"; "xz"; ""; ""; ""];
+         ["tar_in"; "$srcdir/../test-data/files/helloworld.tar.xz"; "/tar_in_xz"; "xz"; ""; ""; ""; ""];
          ["cat"; "/tar_in_xz/hello"]], "hello\n"), []
     ];
     shortdesc = "unpack tarfile to directory";
@@ -2674,6 +2674,12 @@ If set to true, SELinux contexts are restored from the tar file.
 
 If set to true, POSIX ACLs are restored from the tar file.
 
+=item C<keepdirlink>
+
+If set to true, existing symlinks to directories are followed when
+extracting from the tar file.  This is important for usrmerge systems
+where F</lib> is a symlink to F</usr/lib>.
+
 =back|} };
 
   { defaults with