Re: KVM induced panic on 2.6.38[2367] & 2.6.39

Eric Dumazet
2011-06-07T13:37:54Z

Le mardi 07 juin 2011 à 21:27 +0800, Brad Campbell a écrit :
> On 07/06/11 04:22, Eric Dumazet wrote:
>
> > Could you please try latest linux-2.6 tree ?
> >
> > We fixed many networking bugs that could explain your crash.
> >
> >
> >
> >
>
> No good I'm afraid.
>
> [ 543.040056]
> =============================================================================
> [ 543.040136] BUG ip_dst_cache: Padding overwritten.
> 0xffff8803e4217ffe-0xffff8803e4217fff
> [ 543.040194]

Thats pretty strange : These are the last two bytes of a page, set to
0x0000 (a 16 bit value)

There is no way a dst field could actually sit on this location (its a
padding), since a dst is a bit less than 256 bytes (0xe8), and each
entry is aligned on a 64byte address.

grep dst /proc/slabinfo

ip_dst_cache 32823 62944 256 32 2 : tunables 0 0
0 : slabdata 1967 1967 0

sizeof(struct rtable)=0xe8

> -----------------------------------------------------------------------------
> [ 543.040198]
> [ 543.040298] INFO: Slab 0xffffea000d9e74d0 objects=25 used=25 fp=0x
> (null) flags=0x8000000000004081
> [ 543.040364] Pid: 4576, comm: kworker/1:2 Not tainted 3.0.0-rc2 #1
> [ 543.040415] Call Trace:
> [ 543.040472] [<ffffffff810b9c1d>] ? slab_err+0xad/0xd0
> [ 543.040528] [<ffffffff8102e034>] ? check_preempt_wakeup+0xa4/0x160
> [ 543.040595] [<ffffffff810ba206>] ? slab_pad_check+0x126/0x170
> [ 543.040650] [<ffffffff8133045b>] ? dst_destroy+0x8b/0x110
> [ 543.040701] [<ffffffff810ba29a>] ? check_slab+0x4a/0xc0
> [ 543.040753] [<ffffffff810baf2d>] ? free_debug_processing+0x2d/0x250
> [ 543.040808] [<ffffffff810bb27b>] ? __slab_free+0x12b/0x140
> [ 543.040862] [<ffffffff810bbe99>] ? kmem_cache_free+0x99/0xa0
> [ 543.040915] [<ffffffff8133045b>] ? dst_destroy+0x8b/0x110
> [ 543.040967] [<ffffffff813307f6>] ? dst_gc_task+0x196/0x1f0
> [ 543.041021] [<ffffffff8104e954>] ? queue_delayed_work_on+0x154/0x160
> [ 543.041081] [<ffffffff813066fe>] ? do_dbs_timer+0x20e/0x3d0
> [ 543.041133] [<ffffffff81330660>] ? dst_alloc+0x180/0x180
> [ 543.041187] [<ffffffff8104f28b>] ? process_one_work+0xfb/0x3b0
> [ 543.041242] [<ffffffff8104f964>] ? worker_thread+0x144/0x3d0
> [ 543.041296] [<ffffffff8102cc10>] ? __wake_up_common+0x50/0x80
> [ 543.041678] [<ffffffff8104f820>] ? rescuer_thread+0x2e0/0x2e0
> [ 543.041729] [<ffffffff8104f820>] ? rescuer_thread+0x2e0/0x2e0
> [ 543.041782] [<ffffffff81053436>] ? kthread+0x96/0xa0
> [ 543.041835] [<ffffffff813e1d14>] ? kernel_thread_helper+0x4/0x10
> [ 543.041890] [<ffffffff810533a0>] ? kthread_worker_fn+0x120/0x120
> [ 543.041944] [<ffffffff813e1d10>] ? gs_change+0xb/0xb
> [ 543.041993] Padding 0xffff8803e4217f40: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.042718] Padding 0xffff8803e4217f50: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.043433] Padding 0xffff8803e4217f60: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.044155] Padding 0xffff8803e4217f70: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.044866] Padding 0xffff8803e4217f80: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.045590] Padding 0xffff8803e4217f90: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.046311] Padding 0xffff8803e4217fa0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.047034] Padding 0xffff8803e4217fb0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.047755] Padding 0xffff8803e4217fc0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.048474] Padding 0xffff8803e4217fd0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.049203] Padding 0xffff8803e4217fe0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 5a 5a ZZZZZZZZZZZZZZZZ
> [ 543.049909] Padding 0xffff8803e4217ff0: 5a 5a 5a 5a 5a 5a 5a 5a 5a
> 5a 5a 5a 5a 5a 00 00 ZZZZZZZZZZZZZZ..
> [ 543.050021] FIX ip_dst_cache: Restoring
> 0xffff8803e4217f40-0xffff8803e4217fff=0x5a
> [ 543.050021]
>
> Dropped -mm, Hugh and Andrea from CC as this does not appear to be mm or
> ksm related.
>
> I'll pare down the firewall and see if I can make it break easier with a
> smaller test set.

Hmm, not sure now :(

Could you reproduce another bug please ?