[nautilus/gnome-3-26] file: guard against recursive links when emitting change signals

[Carlos Soriano <csoriano src gnome org>]

commit a056ddc904b8540a3e8d1abbb4ae1de6950a6971
Author: Ernestas Kulik <ernestask gnome org>
Date:   Tue Mar 13 16:00:19 2018 +0100

    file: guard against recursive links when emitting change signals
    
    Currently, when propagating file changes, the code recursively notifies
    the files that link to the original file. This quickly falls apart with
    recursive links, as a stack overflow occurs. The fix is only partial,
    however, in that if you try a bit harder, you can still crash Nautilus
    by throwing in another file into the loop (hah).
    
    Fixes https://gitlab.gnome.org/GNOME/nautilus/issues/289

 src/nautilus-file.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)
---
diff --git a/src/nautilus-file.c b/src/nautilus-file.c
index 37f189f8c..5865c3229 100644
--- a/src/nautilus-file.c
+++ b/src/nautilus-file.c
@@ -8581,10 +8581,29 @@ nautilus_file_emit_changed (NautilusFile *file)
     link_files = get_link_files (file);
     for (p = link_files; p != NULL; p = p->next)
     {
-        if (p->data != file)
+        /* Looking for directly recursive links. */
+        g_autolist (NautilusFile) link_targets = NULL;
+        NautilusDirectory *directory;
+
+        if (p->data == file)
+        {
+            continue;
+        }
+
+        link_targets = get_link_files (p->data);
+        directory = nautilus_file_get_directory (p->data);
+
+        /* Reiterating (heh) that this will break with more complex cycles.
+         * Users, stop trying to break things on purpose.
+         */
+        if (g_list_find (link_targets, file) != NULL &&
+            directory == nautilus_file_get_directory (file))
         {
-            nautilus_file_changed (NAUTILUS_FILE (p->data));
+            g_signal_emit (p->data, signals[CHANGED], 0, p->data);
+            continue;
         }
+
+        nautilus_file_changed (NAUTILUS_FILE (p->data));
     }
     nautilus_file_list_free (link_files);
 }