[PATCH] fanotify: Fix event filtering with FAN_ONDIR set

[Suzuki K. Poulose]

From: "Suzuki K. Poulose" <suzuki.poulose@xxxxxxx>

With FAN_ONDIR set, the user can end up getting events, which
it hasn't marked. This was revealed with fanotify04 testcase
failure on Linux-4.0-rc1, and is a regression from 3.19, revealed
with commit (66ba93c0d7fe6: fanotify: don't set FAN_ONDIR implicitly
on a marks ignored mask).

 # /opt/ltp/testcases/bin/fanotify04
 [ ... ]
fanotify04    7  TPASS  :  event generated properly for type 100000
fanotify04    8  TFAIL  :  fanotify04.c:147: got unexpected event 30
fanotify04    9  TPASS  :  No event as expected

The testcase sets the adds the following marks :
	FAN_OPEN | FAN_ONDIR for a fanotify on a dir.
Then does an open(), followed by close() of the directory and
expects to see an event FAN_OPEN(0x20). However, the fanotify
returns (FAN_OPEN|FAN_CLOSE_NOWRITE(0x10)). This happens due
to the flaw in the check for event_mask in fanotify_should_send_event()
which does:

	if (event_mask & marks_mask & ~marks_ignored_mask)
		return true;

where, event_mask = (FAN_ONDIR | FAN_CLOSE_NOWRITE),
       marks_mask = (FAN_ONDIR | FAN_OPEN),
       marks_ignored_mask = 0

Fix this by masking the outgoing events to the user, as we
already take care of FAN_ONDIR and FAN_EVENT_ON_CHILD.

Cc: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Eric Paris <eparis@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@xxxxxxx>
---
 fs/notify/fanotify/fanotify.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 9a66ff7..d2f97ec 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -143,7 +143,8 @@ static bool fanotify_should_send_event(struct fsnotify_mark *inode_mark,
 	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
 		return false;
 
-	if (event_mask & marks_mask & ~marks_ignored_mask)
+	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
+				 ~marks_ignored_mask)
 		return true;
 
 	return false;
-- 
1.7.9.5


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