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SubjectRe: XFS information leak during crash
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/ |
> Specs are a basis for _talking_about_ things. But they are _not_ a basis <
> for implementing software. --Linus Torvalds <
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