[DRBD-user] NULL deref at drbd_submit_peer_request

[Lars Ellenberg]

On Wed, Feb 08, 2017 at 09:00:48AM +0800, Jasmin J. wrote:
> Hi!
> 
> Look to this commit e0645836e870346cafe688cbdd8ec29092f6cdb5 (Tue Nov 8
> 11:43:09 2016) and this d9aea72bb66bb27f815de082d5b347fcddfc9c1b (Thu Nov 10
> 14:48:33 2016) in http://git.linbit.com/drbd-8.4.git/
> 
> I am not sure if this solves your particular problem,

That patch certainly is completely unrelated,
and in this case even irrelevant.

It is a fix for a (potential) sending side bug on kernel >= 4.0.

This is the receiving side,
and kernel 2.6.32 (so not even affected),
and a totally different scenario anyways.

> but you could use the
> newest version 8.4.9-2 and test if it is gone,

Yes. 

> when you have a test scenario
> where it happens easily.
> 
> BR,
>    Jasmin
> 
> *******************************************************************************
> 
> On 02/07/2017 06:28 PM, Tadashi Abe wrote:
> > Hi,
> >
> > I'm using DRBD 8.4.8-1 with linux-2.6.32 kernel, on 2 nodes.
> >
> > # cat /proc/drbd
> > version: 8.4.8-1 (api:1/proto:86-101)
> > GIT-hash: 22b4c802192646e433d3f7399d578ec7fecc6272
> >
> > When running a kind of system test (detach/attach loop in high system load),

"Don't do that, then." :-)
[wonders what real-world scenario that test is supposed to excercise]

> > NULL pointer deref occurs on a node at drbd_submit_peer_request.
> > One thing I notice is the following 2 assertion failure about the same drbd
> > device (drbd6) is seen many times
> > before NULL deref occurs.
> >
> > Jan 18 12:19:29 HOSTA_101 kernel: : [161157.608191] block drbd6: ASSERT( i >= 0 ) in drivers/block/drbd/drbd_int.h:2270
> >
> > These makes me the suspicion that device->local_cnt is invalid count.
> > (the former assertion failure occurs in put_ldev() in drbd code I'm using).
> >
> > Here's syslog snippet of BUG.

> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.600846] BUG: unable to handle kernel NULL pointer dereference at (null)
> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.601807] IP: [<ffffffffa010f07d>] drbd_submit_peer_request+0x8d/0x4c0 [drbd]

> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.852971] Call Trace:
> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.856040] [<ffffffffa01126ab>] receive_RSDataReply+0x13b/0x490 [drbd]
> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.856040] [<ffffffffa0110880>] drbd_receiver+0x100/0x2e0 [drbd]
> > Jan 18 12:20:38 HOSTA_101 kernel: : [161228.856040] [<ffffffffa012476d>] drbd_thread_setup+0x2d/0x110 [drbd]

-- 
: Lars Ellenberg
: LINBIT | Keeping the Digital World Running
: DRBD -- Heartbeat -- Corosync -- Pacemaker

DRBD® and LINBIT® are registered trademarks of LINBIT
__
please don't Cc me, but send to list -- I'm subscribed