fanotify: fix merging marks masks with FAN_ONDIR

mainline inclusion
from mainline-5.7-rc1
commit 55bf882c
category: bugfix
bugzilla: 46764
CVE: NA
https://gitee.com/openeuler/kernel/issues/I27PTB?from=project-issue
---------------------------

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 54a307ba ("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.comSigned-off-by: NAmir Goldstein <amir73il@gmail.com>
Signed-off-by: NJan Kara <jack@suse.cz>

Conflicts:
	fs/notify/fanotify/fanotify.c
Signed-off-by: Nyangerkun <yangerkun@huawei.com>
Reviewed-by: Nzhangyi (F) <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/notify/fanotify/fanotify.c

@@ -117,6 +117,12 @@ static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
 
 		/* Apply ignore mask regardless of ISDIR and ON_CHILD flags */
 		marks_ignored_mask |= mark->ignored_mask;
+		/*
+		 * If the event is on dir and this mark doesn't care about
+		 * events on dir, don't send it!
+		 */
+		if (d_is_dir(path->dentry) && !(mark->mask & FS_ISDIR))
+			continue;
 
 		/*
 		 * If the event is for a child and this mark doesn't care about
@@ -130,10 +136,6 @@ static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
 		marks_mask |= mark->mask;
 	}
 
-	if (d_is_dir(path->dentry) &&
-	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
-		return false;
-
 	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
 				 ~marks_ignored_mask)
 		return true;