[PATCH 5.6 027/161] fanotify: fix ignore mask logic for events on child and on dir

[Greg Kroah-Hartman]

From: Amir Goldstein <amir73il@xxxxxxxxx>

[ Upstream commit 2f02fd3fa13e51713b630164f8a8e5b42de8283b ]

The comments in fanotify_group_event_mask() say:

  "If the event is on dir/child and this mark doesn't care about
   events on dir/child, don't send it!"

Specifically, mount and filesystem marks do not care about events
on child, but they can still specify an ignore mask for those events.
For example, a group that has:
- A mount mark with mask 0 and ignore_mask FAN_OPEN
- An inode mark on a directory with mask FAN_OPEN | FAN_OPEN_EXEC
  with flag FAN_EVENT_ON_CHILD

A child file open for exec would be reported to group with the FAN_OPEN
event despite the fact that FAN_OPEN is in ignore mask of mount mark,
because the mark iteration loop skips over non-inode marks for events
on child when calculating the ignore mask.

Move ignore mask calculation to the top of the iteration loop block
before excluding marks for events on dir/child.

Link: https://lore.kernel.org/r/20200524072441.18258-1-amir73il@xxxxxxxxx
Reported-by: Jan Kara <jack@xxxxxxx>
Link: https://lore.kernel.org/linux-fsdevel/20200521162443.GA26052@xxxxxxxxxxxxxx/
Fixes: 55bf882c7f13 "fanotify: fix merging marks masks with FAN_ONDIR"
Fixes: b469e7e47c8a "fanotify: fix handling of events on child..."
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/notify/fanotify/fanotify.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index deb13f0a0f7d..d24548ed31b9 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -171,6 +171,10 @@ 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];
+
+		/* 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!
@@ -188,7 +192,6 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 			continue;
 
 		marks_mask |= mark->mask;
-		marks_ignored_mask |= mark->ignored_mask;
 	}
 
 	test_mask = event_mask & marks_mask & ~marks_ignored_mask;
-- 
2.25.1