[PATCH 5.6 163/194] fanotify: fix merging marks masks with FAN_ONDIR

Greg Kroah-Hartman
2020-05-18T18:09:01Z

From: Amir Goldstein <amir73il@gmail.com>

commit 55bf882c7f13dda8bbe624040c6d5b4fbb812d16 upstream.

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>
Cc: Rachel Sibley <rasibley@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/notify/fanotify/fanotify.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -172,6 +172,13 @@ static u32 fanotify_group_event_mask(str
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(str
user_mask &= ~FAN_ONDIR;
}

- if (event_mask & FS_ISDIR &&
- !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
- return 0;
-
return test_mask & user_mask;
}