linux-kernel - Re: fanotify - overall design before I start sending patches

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Message-Id: <200908041709.51659.tvrtko.ursulin@sophos.com>
Date:	Tue, 4 Aug 2009 17:09:50 +0100
From:	Tvrtko Ursulin <tvrtko.ursulin@...hos.com>
To:	Eric Paris <eparis@...hat.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
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	Douglas Leeder <douglas.leeder@...hos.com>,
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	"mmorley@....in" <mmorley@....in>, "pavel@...e.cz" <pavel@...e.cz>
Subject: Re: fanotify - overall design before I start sending patches


Hi Eric, all,

On Friday 24 July 2009 21:13:49 Eric Paris wrote:
> If a FAN_ACCESS_PERM or FAN_OPEN_PERM event is received the listener
> must send a response before the 5 second timeout.  If no response is
> sent before the 5 second timeout the original operation is allowed.  If
> this happens too many times (10 in a row) the fanotify group is evicted
> from the kernel and will not get any new events.  Sending a response is

Would it make more sense to deny on timeouts and then evict? I am thinking it 
would be more secure with no significant drawbacks. Also for usages like HSM 
allowing it without data being in place might present wrong content to the 
user.

> The only other current interface is the ability to ignore events by
> superblock magic number.  This makes it easy to ignore all events
> in /proc which can be difficult to accomplish firing FANOTIFY_SET_MARK
> with ignored_masks over and over as processes are created and destroyed.

Just to double-check, that would also work for any other filesystem and is 
controllable from userspace?

Tvrtko
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