fanotify: fix merging marks masks with FAN_ONDIR

Change the logic of FAN_ONDIR in two ways that are similar to the logic
of FAN_EVENT_ON_CHILD, that was fixed in commit 54a307ba8d3c ("fanotify:
fix logic of events on child"):

1. The flag is meaningless in ignore mask
2. The flag refers only to events in the mask of the mark where it is set

This is what the fanotify_mark.2 man page says about FAN_ONDIR:
"Without this flag, only events for files are created."  It doesn't
say anything about setting this flag in ignore mask to stop getting
events on directories nor can I think of any setup where this capability
would be useful.

Currently, when marks masks are merged, the FAN_ONDIR flag set in one
mark affects the events that are set in another mark's mask and this
behavior causes unexpected results.  For example, a user adds a mark on a
directory with mask FAN_ATTRIB | FAN_ONDIR and a mount mark with mask
FAN_OPEN (without FAN_ONDIR).  An opendir() of that directory (which is
inside that mount) generates a FAN_OPEN event even though neither of the
marks requested to get open events on directories.

Link: https://lore.kernel.org/r/20200319151022.31456-10-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 97d34b9..960f4f4 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -171,6 +171,13 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
                if (!fsnotify_iter_should_report_type(iter_info, type))
                        continue;
                mark = iter_info->marks[type];
+               /*
+                * If the event is on dir and this mark doesn't care about
+                * events on dir, don't send it!
+                */
+               if (event_mask & FS_ISDIR && !(mark->mask & FS_ISDIR))
+                       continue;
+
                /*
                 * If the event is for a child and this mark doesn't care about
                 * events on a child, don't send it!
@@ -203,10 +210,6 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
                user_mask &= ~FAN_ONDIR;
        }
 
-       if (event_mask & FS_ISDIR &&
-           !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
-               return 0;
-
        return test_mask & user_mask;
 }