Re: Filesystem Mutation Tool

[Greg KH <greg@kroah.com>]

On Fri, Aug 04, 2006 at 07:07:02PM -0700, Darrick J. Wong wrote:
> Hi all,
> 
> As I might've mentioned to a few of you at OLS, I've hacked up a quick
> and dirty program to study the effects of what happens to a filesystem
> when certain blocks mutate underneath it (think malice, your RAID5
> controller goes berserk, etc).  Said program is now posted in a crude
> form here:
> 
> http://sweaglesw.net/~djwong/programs/fs_mutate/
> 
> I've run this program against ext3 and reiserfs; so far, ext3 seems to
> be the stability winner, as it tends to stay up the longest (about 30-35
> minutes) even with destroy mode turned on.  reiserfs lasts a few minutes
> under such a beating.  Of course, "stays up" is a long way from "works
> properly" -- overwriting things like indirect blocks has the rather
> amusing effect of generating lots of messages about falling off the end
> of a drive.  As with the folks who used carefully crafted ISO9660
> filesystems to crash arbitrary machines demonstrated last year, it's not
> so hard to get Linux to automount filesystems.  To my knowledge,
> nobody's tried a similar thing against the other filesystems, though I
> could just be ignorant.

People have done it in the past, and found lots of bugs that have
hopefully been fixed (although the iso issues have not been fixed...)

> What do you think?  Useful tool?  Or am I the one being the tool? ;)

I think it's useful, especially if it causes things to be fixed up in
the kernel :)

Try running it against a vfat filesystem and see if you can create some
good oopses.  That would be a good place to start, as USB flash sticks
are more common these days than cdroms...

thanks,

greg k-h