Re: Strange kind of corruption on a dm-crypt device

[Oren Held <oren.held@xxxxxxxxx>]

Alright. Problem solved.
As mentioned in Debian's http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=568008, default cipher was changed from aes-cbc-plain to aes-cbc-essiv:sha256, while mine uses the former.

(Still, crypttab should've enforced it, as I had a cipher=aes-cbc-plain  line. I'll update if I find any interesting finding on that)

10x

Oren

On 14 May 2011 18:58, Oren Held <oren.held@xxxxxxxxx> wrote:

Uh; sorry for the messed message.. will re-paste with clean formatting.

----

Hi,

I'm using dm-crypt for 2 years now and it's rather stable. I'm not using luks but only 'cryptsetup create' method. Suddenly this morning, after an unclean shutdown, I've encountered a strange problem:

When I use 'cryptsetup create homes /dev/mapper/myvg-homes' and enter the

passphrase, instead of creating a new dm device with a proper ext4 fs as

it used to, I get a bad device. But not *totally* bad.

Fsck/mount fail to find the superblock. Also no backup superblocks are

available. I did try the 'mkfs -n' for finding the backup superblocks, for

fsck -b, but none of them works.

===================================================

fsck from util-linux-ng 2.17.2

e2fsck 1.41.12 (17-May-2010)

fsck.ext4: Superblock invalid, trying backup blocks...

fsck.ext4: The ext2 superblock is corrupt while trying to open

/dev/mapper/homes

The superblock could not be read or does not describe a correct ext2

filesystem.  If the device is valid and it really contains an ext2

filesystem (and not swap or ufs or something else), then the superblock

is corrupt, and you might try running e2fsck with an alternate superblock:

    e2fsck -b 8193 <device>

===================================================

Why is this case strange? because when I read the device with my naked eye

(or with 'strings' command) I can see lots of plain, *unencrypted* file

content. so it seems like some kind of a limbo, decryption worked, but not

so well...

I'm using Debian unstable (kernel 2.6.38-2), which just got the upgrade package for cryptsetup 1.3.0 yesterday. I'm not sure if my problem has to do with the upgrade, but the timing makes me wonder. I did try downgrading to 1.2.0 and to 2.6.37, but it didn't help.

Any suggestion on how to progress? anybody experienced something similar recently? I'm still not sure if it's a real bug in cryptsetup/dm/kernel, or something broken specifically in my place.

10x

Oren

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