inotify cookie regression/info leak in latest mainline

[Vegard Nossum]

Hi,

It would seem that

commit 7053aee26a3548ebaba046ae2e52396ccf56ac6c
Author: Jan Kara <jack@xxxxxxx>
Date:   Tue Jan 21 15:48:14 2014 -0800

    fsnotify: do not share events between notification groups

introduced a bug where the cookie field of struct inotify_event never 
gets initialised. In particular, it used to be initialised when 
send_to_group() called fsnotify_create_event(), but that no longer 
happens, and the 'cookie' parameter of send_to_group() never gets used.

The problem manifests itself in copy_event_to_user() where the cookie 
field is copied to userspace without being initialised.

I tested this with a simple userspace program, I seem to get mostly 
0xffff8800 in the cookie field for non-move events (which should always 
have 0 here).


Vegard
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