--- /dev/null
+From ed8f2235da7d2a408bfa18c1003f4a07f90b05e8 Mon Sep 17 00:00:00 2001
+From: Philip Withnall <pwithnall@endlessos.org>
+Date: Wed, 24 Feb 2021 17:36:07 +0000
+Subject: [PATCH 4/5] glocalfileoutputstream: Fix CREATE_REPLACE_DESTINATION
+ with symlinks
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+The `G_FILE_CREATE_REPLACE_DESTINATION` flag is equivalent to unlinking
+the destination file and re-creating it from scratch. That did
+previously work, but in the process the code would call `open(O_CREAT)`
+on the file. If the file was a dangling symlink, this would create the
+destination file (empty). That’s not an intended side-effect, and has
+security implications if the symlink is controlled by a lower-privileged
+process.
+
+Fix that by not opening the destination file if it’s a symlink, and
+adjusting the rest of the code to cope with
+ - the fact that `fd == -1` is not an error iff `is_symlink` is true,
+ - and that `original_stat` will contain the `lstat()` results for the
+ symlink now, rather than the `stat()` results for its target (again,
+ iff `is_symlink` is true).
+
+This means that the target of the dangling symlink is no longer created,
+which was the bug. The symlink itself continues to be replaced (as
+before) with the new file — this is the intended behaviour of
+`g_file_replace()`.
+
+The behaviour for non-symlink cases, or cases where the symlink was not
+dangling, should be unchanged.
+
+Includes a unit test.
+
+Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
+
+Fixes: #2325
+
+CVE: CVE-2021-28153
+
+Upstream-Status: Backport [https://gitlab.gnome.org/GNOME/glib/-/issues/2325]
+
+Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
+---
+ gio/glocalfileoutputstream.c | 77 ++++++++++++++++++-------
+ gio/tests/file.c | 108 +++++++++++++++++++++++++++++++++++
+ 2 files changed, 163 insertions(+), 22 deletions(-)
+
+diff --git a/gio/glocalfileoutputstream.c b/gio/glocalfileoutputstream.c
+index 392d0b0..a2c7e3c 100644
+--- a/gio/glocalfileoutputstream.c
++++ b/gio/glocalfileoutputstream.c
+@@ -878,16 +878,22 @@ handle_overwrite_open (const char *filename,
+ /* Could be a symlink, or it could be a regular ELOOP error,
+ * but then the next open will fail too. */
+ is_symlink = TRUE;
+- fd = g_open (filename, open_flags, mode);
++ if (!replace_destination_set)
++ fd = g_open (filename, open_flags, mode);
+ }
+-#else
+- fd = g_open (filename, open_flags, mode);
+- errsv = errno;
++#else /* if !O_NOFOLLOW */
+ /* This is racy, but we do it as soon as possible to minimize the race */
+ is_symlink = g_file_test (filename, G_FILE_TEST_IS_SYMLINK);
++
++ if (!is_symlink || !replace_destination_set)
++ {
++ fd = g_open (filename, open_flags, mode);
++ errsv = errno;
++ }
+ #endif
+
+- if (fd == -1)
++ if (fd == -1 &&
++ (!is_symlink || !replace_destination_set))
+ {
+ char *display_name = g_filename_display_name (filename);
+ g_set_error (error, G_IO_ERROR,
+@@ -898,15 +904,30 @@ handle_overwrite_open (const char *filename,
+ return -1;
+ }
+
+- res = g_local_file_fstat (fd,
+- G_LOCAL_FILE_STAT_FIELD_TYPE |
+- G_LOCAL_FILE_STAT_FIELD_MODE |
+- G_LOCAL_FILE_STAT_FIELD_UID |
+- G_LOCAL_FILE_STAT_FIELD_GID |
+- G_LOCAL_FILE_STAT_FIELD_MTIME |
+- G_LOCAL_FILE_STAT_FIELD_NLINK,
+- G_LOCAL_FILE_STAT_FIELD_ALL, &original_stat);
+- errsv = errno;
++ if (!is_symlink)
++ {
++ res = g_local_file_fstat (fd,
++ G_LOCAL_FILE_STAT_FIELD_TYPE |
++ G_LOCAL_FILE_STAT_FIELD_MODE |
++ G_LOCAL_FILE_STAT_FIELD_UID |
++ G_LOCAL_FILE_STAT_FIELD_GID |
++ G_LOCAL_FILE_STAT_FIELD_MTIME |
++ G_LOCAL_FILE_STAT_FIELD_NLINK,
++ G_LOCAL_FILE_STAT_FIELD_ALL, &original_stat);
++ errsv = errno;
++ }
++ else
++ {
++ res = g_local_file_lstat (filename,
++ G_LOCAL_FILE_STAT_FIELD_TYPE |
++ G_LOCAL_FILE_STAT_FIELD_MODE |
++ G_LOCAL_FILE_STAT_FIELD_UID |
++ G_LOCAL_FILE_STAT_FIELD_GID |
++ G_LOCAL_FILE_STAT_FIELD_MTIME |
++ G_LOCAL_FILE_STAT_FIELD_NLINK,
++ G_LOCAL_FILE_STAT_FIELD_ALL, &original_stat);
++ errsv = errno;
++ }
+
+ if (res != 0)
+ {
+@@ -923,16 +944,27 @@ handle_overwrite_open (const char *filename,
+ if (!S_ISREG (_g_stat_mode (&original_stat)))
+ {
+ if (S_ISDIR (_g_stat_mode (&original_stat)))
+- g_set_error_literal (error,
+- G_IO_ERROR,
+- G_IO_ERROR_IS_DIRECTORY,
+- _("Target file is a directory"));
+- else
+- g_set_error_literal (error,
++ {
++ g_set_error_literal (error,
++ G_IO_ERROR,
++ G_IO_ERROR_IS_DIRECTORY,
++ _("Target file is a directory"));
++ goto err_out;
++ }
++ else if (!is_symlink ||
++#ifdef S_ISLNK
++ !S_ISLNK (_g_stat_mode (&original_stat))
++#else
++ FALSE
++#endif
++ )
++ {
++ g_set_error_literal (error,
+ G_IO_ERROR,
+ G_IO_ERROR_NOT_REGULAR_FILE,
+ _("Target file is not a regular file"));
+- goto err_out;
++ goto err_out;
++ }
+ }
+
+ if (etag != NULL)
+@@ -1015,7 +1047,8 @@ handle_overwrite_open (const char *filename,
+ }
+ }
+
+- g_close (fd, NULL);
++ if (fd >= 0)
++ g_close (fd, NULL);
+ *temp_filename = tmp_filename;
+ return tmpfd;
+ }
+diff --git a/gio/tests/file.c b/gio/tests/file.c
+index 39d51da..ddd1ffc 100644
+--- a/gio/tests/file.c
++++ b/gio/tests/file.c
+@@ -805,6 +805,113 @@ test_replace_cancel (void)
+ g_object_unref (tmpdir);
+ }
+
++static void
++test_replace_symlink (void)
++{
++#ifdef G_OS_UNIX
++ gchar *tmpdir_path = NULL;
++ GFile *tmpdir = NULL, *source_file = NULL, *target_file = NULL;
++ GFileOutputStream *stream = NULL;
++ const gchar *new_contents = "this is a test message which should be written to source and not target";
++ gsize n_written;
++ GFileEnumerator *enumerator = NULL;
++ GFileInfo *info = NULL;
++ gchar *contents = NULL;
++ gsize length = 0;
++ GError *local_error = NULL;
++
++ g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2325");
++ g_test_summary ("Test that G_FILE_CREATE_REPLACE_DESTINATION doesn’t follow symlinks");
++
++ /* Create a fresh, empty working directory. */
++ tmpdir_path = g_dir_make_tmp ("g_file_replace_symlink_XXXXXX", &local_error);
++ g_assert_no_error (local_error);
++ tmpdir = g_file_new_for_path (tmpdir_path);
++
++ g_test_message ("Using temporary directory %s", tmpdir_path);
++ g_free (tmpdir_path);
++
++ /* Create symlink `source` which points to `target`. */
++ source_file = g_file_get_child (tmpdir, "source");
++ target_file = g_file_get_child (tmpdir, "target");
++ g_file_make_symbolic_link (source_file, "target", NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ /* Ensure that `target` doesn’t exist */
++ g_assert_false (g_file_query_exists (target_file, NULL));
++
++ /* Replace the `source` symlink with a regular file using
++ * %G_FILE_CREATE_REPLACE_DESTINATION, which should replace it *without*
++ * following the symlink */
++ stream = g_file_replace (source_file, NULL, FALSE /* no backup */,
++ G_FILE_CREATE_REPLACE_DESTINATION, NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ g_output_stream_write_all (G_OUTPUT_STREAM (stream), new_contents, strlen (new_contents),
++ &n_written, NULL, &local_error);
++ g_assert_no_error (local_error);
++ g_assert_cmpint (n_written, ==, strlen (new_contents));
++
++ g_output_stream_close (G_OUTPUT_STREAM (stream), NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ g_clear_object (&stream);
++
++ /* At this point, there should still only be one file: `source`. It should
++ * now be a regular file. `target` should not exist. */
++ enumerator = g_file_enumerate_children (tmpdir,
++ G_FILE_ATTRIBUTE_STANDARD_NAME ","
++ G_FILE_ATTRIBUTE_STANDARD_TYPE,
++ G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS, NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ info = g_file_enumerator_next_file (enumerator, NULL, &local_error);
++ g_assert_no_error (local_error);
++ g_assert_nonnull (info);
++
++ g_assert_cmpstr (g_file_info_get_name (info), ==, "source");
++ g_assert_cmpint (g_file_info_get_file_type (info), ==, G_FILE_TYPE_REGULAR);
++
++ g_clear_object (&info);
++
++ info = g_file_enumerator_next_file (enumerator, NULL, &local_error);
++ g_assert_no_error (local_error);
++ g_assert_null (info);
++
++ g_file_enumerator_close (enumerator, NULL, &local_error);
++ g_assert_no_error (local_error);
++ g_clear_object (&enumerator);
++
++ /* Double-check that `target` doesn’t exist */
++ g_assert_false (g_file_query_exists (target_file, NULL));
++
++ /* Check the content of `source`. */
++ g_file_load_contents (source_file,
++ NULL,
++ &contents,
++ &length,
++ NULL,
++ &local_error);
++ g_assert_no_error (local_error);
++ g_assert_cmpstr (contents, ==, new_contents);
++ g_assert_cmpuint (length, ==, strlen (new_contents));
++ g_free (contents);
++
++ /* Tidy up. */
++ g_file_delete (source_file, NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ g_file_delete (tmpdir, NULL, &local_error);
++ g_assert_no_error (local_error);
++
++ g_clear_object (&target_file);
++ g_clear_object (&source_file);
++ g_clear_object (&tmpdir);
++#else /* if !G_OS_UNIX */
++ g_test_skip ("Symlink replacement tests can only be run on Unix")
++#endif
++}
++
+ static void
+ on_file_deleted (GObject *object,
+ GAsyncResult *result,
+@@ -1798,6 +1905,7 @@ main (int argc, char *argv[])
+ g_test_add_data_func ("/file/async-create-delete/4096", GINT_TO_POINTER (4096), test_create_delete);
+ g_test_add_func ("/file/replace-load", test_replace_load);
+ g_test_add_func ("/file/replace-cancel", test_replace_cancel);
++ g_test_add_func ("/file/replace-symlink", test_replace_symlink);
+ g_test_add_func ("/file/async-delete", test_async_delete);
+ g_test_add_func ("/file/copy-preserve-mode", test_copy_preserve_mode);
+ g_test_add_func ("/file/measure", test_measure);
+--
+2.17.1
+
