linux-kernel - [PATCH 5.6 163/194] fanotify: fix merging marks masks with FAN

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Date:   Mon, 18 May 2020 19:37:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Amir Goldstein <amir73il@...il.com>,
        Jan Kara <jack@...e.cz>, Rachel Sibley <rasibley@...hat.com>
Subject: [PATCH 5.6 163/194] fanotify: fix merging marks masks with FAN_ONDIR

From: Amir Goldstein <amir73il@...il.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@...il.com>
Signed-off-by: Jan Kara <jack@...e.cz>
Cc: Rachel Sibley <rasibley@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;
 }