Bug#664088: mdadm fails to initialize components for bitmap

[Michael Tokarev]

On 13.04.2012 00:22, Markus Hochholdinger wrote:
> Hello Michael,
> 
> Am 12.04.2012 um 21:38 Uhr schrieb Michael Tokarev <mjt at tls.msk.ru>:
>> On 31.03.2012 01:28, Markus Hochholdinger wrote:
>>> Package: mdadm
>>> Version: 3.2.3-2
>>> Followup-For: Bug #664088
>>> Dear Maintainer,
>>> seems I've been stumbled over this bug. I'm running wheezy and can
>>> reproduce a crash: mdadm --grow /dev/md0 --bitmap=none
>>> mdadm --grow /dev/md0 --bitmap=internal
>>> A few seconds after this, the system is still alive, I see the newly
>>> created bitmap in /proc/mdstat, and then the system crashes: [ 
>>> 342.437949] md0: bitmap file is out of date (0 < 322) -- forcing full
>>> recovery [  342.437967] created bitmap (1 pages) for device md0
>>> [  347.949946] BUG: unable to handle kernel NULL pointer dereference at
>>> 00000008 [  347.949969] IP: [<eda5edbd>] bitmap_endwrite+0x138/0x199
>>> [md_mod] [  347.949991] *pdpt = 0000000002660007 *pde = 0000000000000000
>>> [  347.950010] Oops: 0000 [#1] SMP

>> Oh.  This is a kernel bug, kernel should not crash like this even if
>> incorrect bitmap is created.
>> Marcus, what's your kernel version?
> 
> Linux 3.2.0-2-686-pae from wheezy.

This was obvious from your initial message, but I wasn't clear.
I meant to ask what kernel PACKAGE version is that.

Sigh, how many times I suggested kernel folks to include debian
package version in the kernel OOPs test, but has been ignored
every time... :(

> Hm, perhaps I could use mdadm from squeeze to check weather the kernel also 
> crashes.

I doubt it is easily reproducible.  The original bug in mdadm (which is
fixed upstream btw, in git, not any released version) does not initialize
bitmap, leaving some garbage in it.  Obviously not every garbage triggers
the bug in kernel.  So if another attempt will not crash your kernel it
does not tell anything.

I asked for the kernel package version in order to clone and reassign
this bugreport to kernel properly.

Thanks!

/mjt