[DRBD-user] in-kernel buffer overflow reading /proc/drbd

Lars Ellenberg Lars.Ellenberg at linbit.com
Fri Aug 20 15:12:31 CEST 2004


/ 2004-08-20 13:47:56 +0200
\ Stephan Rattai:
> Hi everybody,
> 
> I got a little problem with drbd 0.7.2 and kernel 2.6.8.1. During a resync I 
> did 'cat /proc/drbd' and got 
> 
> version: 0.7.2 (api:75/proto:74)
> SVN Revision: 1483:1485 build by pete at bonnie, 2004-08-17 17:17:07
>  0: cs:SyncSource st:Primary/Secondary ld:Consistent
>     ns:22933688 nr:0 dw:0 dr:22933688 al:0 bm:1400 lo:0 pe:0 ua:0 ap:0
>         [>.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
> 
> each time (I tried several times).
> 
> A few seconds later the machine wasn't reachable anymore- it decided it would 
> be a good idea to reboot. The last sign of living was: 
> 
> Aug 20 13:14:46 bonnie kernel: drbd0: Resync started as SyncSource (need to 
> sync 11819424 KB [2954856 bits set]).
> Aug 20 13:23:32 bonnie kernel: drbd0: ASSERT( rs_left < mdev->rs_total ) 
> in /root/src/drbd-0.7.2/drbd/drbd_proc.c:70
> Aug 20 13:23:32 bonnie kernel: proc_file_read: Apparent buffer overflow!
> 
> The last two messages appeared about 20 times.

hm...
I replaced that ASSERT with an appropriate if branch in svn now.
so I prevent the buffer overflow.
but... this just masks the logic bug that is hidden elsewhere.
most likely its "only" some race somewhere, two assignments in the
"wrong" order or some such. We'll investigate.

may I ask some more system details:
 cpus, storage device size, ...


	Lars Ellenberg

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