linux-kernel - Re: [malware-list] TALPA - a threat model? well sorta.

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Date:	Thu, 14 Aug 2008 19:34:30 -0400
From:	Theodore Tso <tytso@....edu>
To:	"J. Bruce Fields" <bfields@...ldses.org>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Eric Paris <eparis@...hat.com>, tvrtko.ursulin@...hos.com,
	alan@...rguk.ukuu.org.uk, andi@...stfloor.org,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, malware-list@...ts.printk.net,
	malware-list-bounces@...sg.printk.net, peterz@...radead.org,
	viro@...IV.linux.org.uk
Subject: Re: [malware-list] TALPA - a threat model?  well sorta.

On Thu, Aug 14, 2008 at 05:21:09PM -0400, J. Bruce Fields wrote:
> > I have not yet seen code actually using it at all, neither in mainline
> > nor on one of the many nfs development lists.
> 
> Oops, I'd love to, and it should be very easy.  How do I find out if
> i_version is supported on a given superblock?

We don't have a way of exporting this fact at the moment.  I assume
the best way would be to add a flag in struct super.

> There's nothing particularly "advanced" about this, by the way--this is
> a very minor variation on the caching model that nfs has always had, and
> our nfsv4 server is currently pretty broken without it.

Well, if you're willing to try it out, as I've mentioned on my
blog[1][2], ext4 is working pretty well on my laptop --- I'm running
it as my primary filesystem.  There are a few problems with ext3
filesystems converted to use ext4, as opposed to starting afresh via
"mke2fs -t ext4dev /dev/hdXX" that we've just found in the past week
(and fixed within a day or two, although they haven't been pushed to
Linus yet), but overall, it's been pretty stable.

So this would be a good time for someone who is familiar wiht NFSv4 to
try it out and let us know if the i_version support is as you would
like in ext4 --- we're in the bugfixing/stablization phase right now,
so this would be an ideal time to get that feedback.  For more
information, on how to get started, please see:

http://ext4.wiki.kernel.org/index.php/Ext4_Howto

for instructions, and mount the filesystem with the "-o i_version"
mount option.

> Actually, it's pretty broken even on nfsv2/v3 for filesystems with poor
> time resolution.

And that's fixed in ext4 as well....

						- Ted

[1] http://thunk.org/tytso/blog/2008/06/30/ext4-is-now-the-primary-filesystem-on-my-laptop/
[2] http://thunk.org/tytso/blog/2008/08/08/fast-ext4-fsck-times/

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