fanotify: report parent fid + child fid

Add support for FAN_REPORT_FID | FAN_REPORT_DIR_FID.
Internally, it is implemented as a private case of reporting both
parent and child fids and name, the parent and child fids are recorded
in a variable length fanotify_name_event, but there is no name.

It should be noted that directory modification events are recorded
in fixed size fanotify_fid_event when not reporting name, just like
with group flags FAN_REPORT_FID.

Link: https://lore.kernel.org/r/20200716084230.30611-23-amir73il@gmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 4d1eddd..bd9e88e 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -535,7 +535,7 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
                /*
                 * With both flags FAN_REPORT_DIR_FID and FAN_REPORT_FID, we
                 * report the child fid for events reported on a non-dir child
-                * in addition to reporting the parent fid and child name.
+                * in addition to reporting the parent fid and maybe child name.
                 */
                if ((fid_mode & FAN_REPORT_FID) &&
                    id != dirid && !(mask & FAN_ONDIR))
@@ -552,11 +552,17 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
                 *
                 * For event on non-directory that is reported to parent, we
                 * record the fid of the parent and the name of the child.
+                *
+                * Even if not reporting name, we need a variable length
+                * fanotify_name_event if reporting both parent and child fids.
                 */
-               if ((fid_mode & FAN_REPORT_NAME) &&
-                   ((mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
-                    !(mask & FAN_ONDIR)))
+               if (!(fid_mode & FAN_REPORT_NAME)) {
+                       name_event = !!child;
+                       file_name = NULL;
+               } else if ((mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||
+                          !(mask & FAN_ONDIR)) {
                        name_event = true;
+               }
        }
 
        /*
@@ -575,7 +581,7 @@ static struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
 
        if (fanotify_is_perm_event(mask)) {
                event = fanotify_alloc_perm_event(path, gfp);
-       } else if (name_event && file_name) {
+       } else if (name_event && (file_name || child)) {
                event = fanotify_alloc_name_event(id, fsid, file_name, child,
                                                  gfp);
        } else if (fid_mode) {

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index be328d7..559de31 100644 (file)
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -371,7 +371,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
 
        /* Event info records order is: dir fid + name, child fid */
        if (fanotify_event_dir_fh_len(event)) {
-               info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;
+               info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
+                                            FAN_EVENT_INFO_TYPE_DFID;
                ret = copy_info_to_user(fanotify_event_fsid(event),
                                        fanotify_info_dir_fh(info),
                                        info_type, fanotify_info_name(info),
@@ -957,18 +958,10 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 
        /*
         * Child name is reported with parent fid so requires dir fid.
-        * If reporting child name, we can report both child fid and dir fid.
+        * We can report both child fid and dir fid with or without name.
         */
-       switch (fid_mode) {
-       case 0:
-       case FAN_REPORT_FID:
-       case FAN_REPORT_DIR_FID:
-       case FAN_REPORT_DFID_NAME:
-       case FAN_REPORT_DFID_NAME | FAN_REPORT_FID:
-               break;
-       default:
+       if ((fid_mode & FAN_REPORT_NAME) && !(fid_mode & FAN_REPORT_DIR_FID))
                return -EINVAL;
-       }
 
        user = get_current_user();
        if (atomic_read(&user->fanotify_listeners) > FANOTIFY_DEFAULT_MAX_LISTENERS) {