Re: [dm-devel] Re: NULL data pointer dereference in kcryptd

[Michael Buesch <mb@bu3sch.de>]

On Saturday 01 August 2009 12:07:12 Michael Buesch wrote:
> On Saturday 01 August 2009 11:04:11 Milan Broz wrote:
> > Herbert Xu wrote:
> > > On Fri, Jul 31, 2009 at 10:54:45PM +0200, Michael Buesch wrote:
> > >> [15577.988608] NIP [c0000000000b8034] .mempool_alloc+0x74/0x1a0
> > >> [15577.988614] LR [c000000000139bdc] .bio_alloc_bioset+0x4c/0x130
> > >> [15577.988616] Call Trace:
> > >> [15577.988619] [c0000001f022fb60] [c0000001f022fbf0] 0xc0000001f022fbf0 (unreliable)
> > >> [15577.988625] [c0000001f022fc40] [c000000000139bdc] .bio_alloc_bioset+0x4c/0x130
> > >> [15577.988632] [c0000001f022fcf0] [c0000000005334a0] .kcryptd_crypt+0x210/0x520
> > >> [15577.988637] [c0000001f022fde0] [c000000000068018] .worker_thread+0x248/0x3e0
> > >> [15577.988642] [c0000001f022ff00] [c00000000006e1e4] .kthread+0x84/0xe0
> > >> [15577.988648] [c0000001f022ff90] [c000000000021830] .kernel_thread+0x54/0x70
> > 
> > That seems like mempool is NULL in bio_alloc_bioset. That mempool/bioset is destroyed only
> > when crypt mapping is destroyed, after workqueue is flushed, so it should not happen...
> > 
> > Which command did you exactly run to trigger this? only sync & mkfs on existing
> > LUKS device or there was also some cryptsetup luksClose (or something removing
> > mapping) before?
> 
> I started mke2fs on a large luks mapping (1TB). So that takes quite a while.
> So I had some time to do some other stuff simultaneously. It happens that I
> did a "sync" while the mke2fs command was still running. The sync immediately froze.
> Then after mke2fs finished writing the inode tables it also froze.
> Then I looked into dmesg and saw the oops.
> I don't think I did a cryptsetup action while mke2fs was running. I just mounted a few
> USB sticks and copied a few files around and did that sync operation...

Of course, I do not know _when_ it oopsed exactly. I may have oopsed even before I started mke2fs
and I did only notice later (due to the stuck processes).
So before doing the mke2fs I did a few luksOpen and luksClose, of course.


-- 
Greetings, Michael.