[Pkg-cryptsetup-devel] Bug#403426: kernel corrupts LUKS partition header on arm

[Gordon Farquharson]

Hi Martin

On 4/26/07, Martin Michlmayr <tbm at cyrius.com> wrote:
> Gordon, can you check if LUKS still doesn't work under heavy load with
> 2.6.21 (I can give you .debs if you want)?

Unfortunately, I can still trigger the problem, although instead of
cryptsetup asking me for the passphrase three times and then returning
"Command failed: No key available with this passphrase", it now just
fails with "Command failed". The problem is intermittent though. Below
are some examples of trying to access the LUKS partition under heavy
load. In the first case, the access works, but then a little while
later, it fails. In the third case, it works again. I sure that the
second case was not a case of typing in the passphrase incorrectly
because the problem is repeatable as shown in the forth case.

gordon at LKG7102D7:~$ uname -a
Linux LKG7102D7 2.6.21-1-ixp4xx #1 Thu Apr 26 20:40:53 MDT 2007
armv5tel GNU/Linux

gordon at LKG7102D7:~$ uptime
 08:57:11 up  9:19,  3 users,  load average: 3.94, 1.54, 0.81
gordon at LKG7102D7:~$ sudo cryptsetup luksOpen /dev/sda2 x
Enter LUKS passphrase:
key slot 0 unlocked.
Command successful.
gordon at LKG7102D7:~$ sudo cryptsetup luksClose x
gordon at LKG7102D7:~$ uptime
 08:57:49 up  9:20,  3 users,  load average: 4.79, 2.05, 1.01

gordon at LKG7102D7:~$ uptime
 09:04:02 up  9:26,  3 users,  load average: 3.93, 3.46, 1.98
gordon at LKG7102D7:~$ sudo cryptsetup luksOpen /dev/sda2 x
Enter LUKS passphrase:
Command failed.
gordon at LKG7102D7:~$ uptime
 09:04:29 up  9:27,  3 users,  load average: 4.29, 3.57, 2.06

gordon at LKG7102D7:~$ uptime
 09:06:35 up  9:29,  3 users,  load average: 2.27, 3.01, 2.03
gordon at LKG7102D7:~$ sudo cryptsetup luksOpen /dev/sda2 x
Enter LUKS passphrase:
key slot 0 unlocked.
Command successful.
gordon at LKG7102D7:~$ uptime
 09:07:14 up  9:29,  3 users,  load average: 2.61, 2.99, 2.07

gordon at LKG7102D7:~$ uptime
 09:18:58 up  9:41,  3 users,  load average: 2.52, 2.47, 2.17
gordon at LKG7102D7:~$ sudo cryptsetup luksOpen /dev/sda2 x
Enter LUKS passphrase:
Command failed.
gordon at LKG7102D7:~$ uptime
 09:19:31 up  9:42,  3 users,  load average: 3.18, 2.63, 2.23

To trigger the heavy load conditions, I am compiling apt on the NSLU2.
Occasionally, to up the load on the NSLU2, I run Linus's test program
that he used to track down the mmap problem, but the problem does
trigger if I am just compiling apt. Also, the load does not need to be
that high to trigger the problem:

gordon at LKG7102D7:~$ uptime
 09:24:12 up  9:46,  3 users,  load average: 1.93, 2.26, 2.17
gordon at LKG7102D7:~$ sudo cryptsetup luksOpen /dev/sda2 x
Enter LUKS passphrase:
Command failed.
gordon at LKG7102D7:~$ uptime
 09:25:35 up  9:48,  3 users,  load average: 1.69, 2.13, 2.13
gordon at LKG7102D7:~$ free
             total       used       free     shared    buffers     cached
Mem:         29912      28800       1112          0        104       4640
-/+ buffers/cache:      24056       5856
Swap:        88316      18640      69676

I have not been able to get the problem to occur under light load conditions.

This problem looks like it is going to be a tricky one to track down.

Gordon

-- 
Gordon Farquharson