Date:	Tue, 29 Apr 2008 12:37:41 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	htmldeveloper@...il.com, bugme-daemon@...zilla.kernel.org,
	netdev@...r.kernel.org, Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [Bug 10575] New: WARNING: at mm/slub.c:2444

On Tue, 29 Apr 2008 21:14:46 +0200
Patrick McHardy <kaber@...sh.net> wrote:

> Andrew Morton wrote:
> > (switched to email.  Please respond via emailed reply-to-all, not via the
> > bugzilla web interface).
> >
> > On Tue, 29 Apr 2008 06:31:36 -0700 (PDT) bugme-daemon@...zilla.kernel.org wrote:
> >
> >   
> >>
> >> kernel version:
> >>
> >> cat include/config/kernel.release 
> >> 2.6.25-sched-devel.git-x86-latest.git
> >>
> >> Shutting down the system generated the following errors:
> >>
> >> Apr 28 00:20:22 funnyman libvirtd: Shutting down on signal 15
> >> Apr 28 00:20:25 funnyman kernel: sky2 eth0: Link is down.
> >> Apr 28 00:20:25 funnyman xinetd[3373]: Exiting...
> >> Apr 28 00:20:30 funnyman kernel: ------------[ cut here ]------------
> >> Apr 28 00:20:30 funnyman kernel: WARNING: at mm/slub.c:2444
> >> kmem_cache_destroy+0xfe/0x108()
> >> Apr 28 00:20:30 funnyman kernel: Modules linked in: rfcomm hidp l2cap bluetooth
> >> button ext2 btrfs hfsplus usb_storage nls_utf8 bridge autofs4 nf_conntrack(-)
> >> xt_tcpudp x_tables sunrpc loop dm_multipath video output sbs sbshc battery ac
> >> ipv6 parport_pc lp parport snd_usb_audio snd_usb_lib snd_rawmidi snd_hwdep
> >> snd_hda_intel snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq
> >> snd_seq_device snd_pcm_oss sg firewire_ohci snd_mixer_oss snd_pcm firewire_core
> >> crc_itu_t snd_timer snd pata_jmicron soundcore serio_raw sky2 snd_page_alloc
> >> pcspkr i2c_i801 iTCO_wdt iTCO_vendor_support i2c_core floppy dm_snapshot
> >> dm_zero dm_mirror dm_mod ahci ata_generic ata_piix libata sd_mod scsi_mod ext3
> >> jbd ehci_hcd ohci_hcd uhci_hcd [last unloaded: xt_state]
> >> Apr 28 00:20:30 funnyman kernel: Pid: 11669, comm: modprobe Not tainted
> >> 2.6.25-sched-devel.git-x86-latest.git #1
> >> Apr 28 00:20:30 funnyman kernel:  [<c042bad6>] warn_on_slowpath+0x46/0x56
> >> Apr 28 00:20:30 funnyman kernel:  [<c0415a33>] ? apic_wait_icr_idle+0x16/0x1d
> >> Apr 28 00:20:30 funnyman kernel:  [<c0415243>] ?
> >> __send_IPI_dest_field+0x50/0x54
> >> Apr 28 00:20:30 funnyman kernel:  [<c04020e5>] ? send_IPI_mask+0xd/0xf
> >> Apr 28 00:20:30 funnyman kernel:  [<c046773c>] ?
> >> get_pageblock_flags_group+0x50/0x6e
> >> Apr 28 00:20:30 funnyman kernel:  [<c046777e>] ?
> >> get_pageblock_migratetype+0x24/0x27
> >> Apr 28 00:20:30 funnyman kernel:  [<c0468472>] ? free_hot_page+0xf/0x11
> >> Apr 28 00:20:30 funnyman kernel:  [<c0468494>] ? __free_pages+0x20/0x2b
> >> Apr 28 00:20:30 funnyman kernel:  [<c047f471>] ? __free_slab+0xac/0xb4
> >> Apr 28 00:20:30 funnyman kernel:  [<c0480754>] kmem_cache_destroy+0xfe/0x108
> >> Apr 28 00:20:30 funnyman kernel:  [<f8d337c0>] nf_conntrack_cleanup+0x53/0x7a
> >> [nf_conntrack]
> >> Apr 28 00:20:30 funnyman kernel:  [<f8d3766d>]
> >> nf_conntrack_standalone_fini+0x1c/0x1e [nf_conntrack]
> >> Apr 28 00:20:30 funnyman kernel:  [<c044b56f>] sys_delete_module+0x177/0x1af
> >> Apr 28 00:20:30 funnyman kernel:  [<c0472c00>] ? remove_vma+0x31/0x53
> >> Apr 28 00:20:30 funnyman kernel:  [<c0473468>] ? do_munmap+0x182/0x19c
> >> Apr 28 00:20:30 funnyman kernel:  [<c0404bae>] sysenter_past_esp+0x6a/0x90
> >> Apr 28 00:20:30 funnyman kernel:  [<c0640000>] ? pci_scan_bridge+0x1dc/0x2eb
> >> Apr 28 00:20:30 funnyman hcid[9436]: Got disconnected from the system message
> >> bus
> >> Apr 28 00:20:30 funnyman kernel:  =======================
> >> Apr 28 00:20:30 funnyman rpc.statd[2994]: Caught signal 15, un-registering and
> >> exiting.
> >> Apr 28 00:20:30 funnyman kernel: ---[ end trace eb2ec02455daeda8 ]---
> >> Apr 28 00:20:30 funnyman portmap[11769]: connect from 127.0.0.1 to
> >> unset(status): request from unprivileged port
> >> Apr 28 00:20:30 funnyman pcscd: pcscdaemon.c:529:signal_trap() Preparing for
> >> suicide
> >>
> >> and mm/slub.c:2444 are as follows:
> >>
> >>  2433  * Close a cache and release the kmem_cache structure
> >>    2434  * (must be used for caches created using kmem_cache_create)
> >>    2435  */
> >>    2436 void kmem_cache_destroy(struct kmem_cache *s)
> >>    2437 {
> >>    2438         down_write(&slub_lock);
> >>    2439         s->refcount--;
> >>    2440         if (!s->refcount) {
> >>    2441                 list_del(&s->list);
> >>    2442                 up_write(&slub_lock);
> >>    2443                 if (kmem_cache_close(s))
> >>    2444                         WARN_ON(1);
> >>    2445                 sysfs_slab_remove(s);
> >>    2446         } else
> >>    2447                 up_write(&slub_lock);
> >>    2448 }
> >>    2449 EXPORT_SYMBOL(kmem_cache_destroy);
> >>
> >> How to reproduce:
> >>
> >> Not sure how, as it occur during shutdown.
> >>     
> >
> > Looks like nf_contrack is destroying a slab cache which still has
> > live objects.
> >
> > I think this came up a few days ago but I'm not sure if it was fixed?
> 
> I believe Stephen fixed a use-after-free in bridging a few days ago,
> are you referring to this? Otherwise a pointer would be appreciated.

<checks>

Sorry, I confused it with a similar-looking USB trace.  Pekka added some
additional debug at that site which might help here - it will tell us the
name of the slab cache:

void kmem_cache_destroy(struct kmem_cache *s)
{
	down_write(&slub_lock);
	s->refcount--;
	if (!s->refcount) {
		list_del(&s->list);
		up_write(&slub_lock);
		if (kmem_cache_close(s)) {
			printk(KERN_ERR "SLUB %s: %s called for cache that "
				"still has objects.\n", s->name, __func__);
			dump_stack();
		}
		sysfs_slab_remove(s);
	} else
		up_write(&slub_lock);
}
			
that was merged into mainline yesterday.

> In any case, htmldeveloper, could you provide some more information
> about your setup, i.e. firewall rules, does the unload happen during
> load, ...? Did you also notice the bug on other kernel versions than
> sched-devel.git-x86-latest.git? Thanks.
> 
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