linux-kernel - Re: [malware-list] scanner interface proposal was: [TALPA] Intro to a linux interface for on access scanning

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Message-ID: <20080818163148.0ef3e383@lxorguk.ukuu.org.uk>
Date:	Mon, 18 Aug 2008 16:31:48 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	tvrtko.ursulin@...hos.com
Cc:	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Adrian Bunk <bunk@...nel.org>, capibara@...all.nl,
	Casey Schaufler <casey@...aufler-ca.com>, davecb@....com,
	david@...g.hm, linux-kernel <linux-kernel@...r.kernel.org>,
	linux-security-module@...r.kernel.org,
	malware-list@...ts.printk.net,
	malware-list-bounces@...sg.printk.net,
	Mihai Don??u <mdontu@...defender.com>,
	Peter Dolding <oiaohm@...il.com>, Pavel Machek <pavel@...e.cz>,
	rmeijer@...all.nl
Subject: Re: [malware-list] scanner interface proposal was: [TALPA] Intro	to
 a linux interface for on access scanning

> Huh? I was never advocating re-scan after each modification and I even 
> explicitly said it does not make sense for AV not only for performance but 
> because it will be useless most of the time. I thought sending out 
> modified notification on close makes sense because it is a natural point, 
> unless someone is trying to subvert which is out of scope. Other have 
> suggested time delay and lumping up.

You need a bit more than close I imagine, otherwise I can simply keep the
file open forever. There are lots of cases where that would be natural
behaviour - eg if I was to attack some kind of web forum and insert a
windows worm into the forum which was database backed the file would
probably never be closed. That seems to be one of the more common attack
vectors nowdays.

> 
> Also, just to double-check, you don't think AV scanning would read the 
> whole file on every write?

So you need the system to accumulate some kind of complete in memory set
of 'dirty' range lists on all I/O ? That is going to have pretty bad
performance impacts and serialization.
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