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Date: Wed, 9 Nov 2005 17:55:39 +0100
From: Jan Kasprzak <kas@fi.muni.cz>
To: Nathan Scott <nathans@sgi.com>
Cc: linux-kernel@vger.kernel.org, linux-xfs@oss.sgi.com
Subject: Re: XFS information leak during crash
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Jan Kasprzak wrote:
: Nathan Scott wrote:
: : 
: : This issue affects every filesystem, right?  Or are you claiming its
: : only XFS affected here?  Have you run your parallel-buffered-writers
: : test case on any other filesystems?  I'd be interested in the results,
: : in particular, with all of the data=xxx modes of other filesystems.
: : 
: 	I will do this tomorrow or the day after and post the results.
:
	Sorry for the delay - I did the test on other filesystems
as well: "random" (i.e. not rewritten) data after the hard reset were
inside the files in the following filesystems:

XFS
ext3 data=writeback
JFS

and my test program did not manage to put those "random" blocks into the
files when running on ext3 with data=ordered mode (as expected).

	I have tried ReiserFS as well, with mixed results:

- when I hit "reset" soon enough (but well after the HDD LED starts
	blinking), I end up with an empty directory after the reboot.
	It seems ReiserFS caches the filesystem operations much longer
	than other filesystems.
- I have not seen truly random data in the files on ReiserFS after the
	hard reset, but I have seen blocks of zeros instead of either
	old or new data. This may be a pure coincidence, so ReiserFS
	may belong to the same group as ext3 with data=writeback mode,
	but I was not able to make the files contain truly random
	blocks by hitting the reset button.

	So, does ReiserFS do some kind of data journaling/ordering as well?

-Yenya

-- 
| Jan "Yenya" Kasprzak  <kas at {fi.muni.cz - work | yenya.net - private}> |
| GPG: ID 1024/D3498839      Fingerprint 0D99A7FB206605D7 8B35FCDE05B18A5E |
| http://www.fi.muni.cz/~kas/    Journal: http://www.fi.muni.cz/~kas/blog/ |
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