Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752627Ab3F0HPv (ORCPT ); Thu, 27 Jun 2013 03:15:51 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:44224 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752240Ab3F0HPs (ORCPT ); Thu, 27 Jun 2013 03:15:48 -0400 Message-ID: <51CBE695.9010207@oracle.com> Date: Thu, 27 Jun 2013 15:15:33 +0800 From: Joe Jin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 MIME-Version: 1.0 To: Eric Dumazet CC: Frank Blaschka , "David S. Miller" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "zheng.x.li@oracle.com" Subject: Re: kernel panic in skb_copy_bits References: <51CBAA48.3080802@oracle.com> <1372311118.3301.214.camel@edumazet-glaptop> In-Reply-To: <1372311118.3301.214.camel@edumazet-glaptop> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6599 Lines: 125 Hi Eric, Thanks for you response, will test it and get back to you. Regards, Joe On 06/27/13 13:31, Eric Dumazet wrote: > On Thu, 2013-06-27 at 10:58 +0800, Joe Jin wrote: >> Hi, >> >> When we do fail over test with iscsi + multipath by reset the switches >> on OVM(2.6.39) we hit the panic: >> >> BUG: unable to handle kernel paging request at ffff88006d9e8d48 >> IP: [] memcpy+0xb/0x120 >> PGD 1798067 PUD 1fd2067 PMD 213f067 PTE 0 >> Oops: 0000 [#1] SMP >> CPU 7 >> Modules linked in: dm_nfs tun nfs fscache auth_rpcgss nfs_acl xen_blkback xen_netback xen_gntdev xen_evtchn lockd sunrpc bridge stp llc bonding be2iscsi iscsi_boot_sysfs ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp bnx2i cnic uio ipv6 cxgb3i libcxgbi cxgb3 mdio dm_round_robin dm_multipath libiscsi_tcp libiscsi scsi_transport_iscsi xenfs xen_privcmd video sbs sbshc acpi_memhotplug acpi_ipmi ipmi_msghandler parport_pc lp parport ixgbe dca sr_mod cdrom bnx2 radeon ttm drm_kms_helper drm snd_seq_dummy i2c_algo_bit i2c_core snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss serio_raw snd_pcm snd_timer snd soundcore snd_page_alloc iTCO_wdt pcspkr iTCO_vendor_support pata_acpi dcdbas i5k_amb ata_generic hwmon floppy ghes i5000_edac edac_core hed dm_snapshot dm_zero dm_mirror dm_region_hash dm_log dm_mod usb_storage lpfc scsi_transport_fc scsi_tgt ata_piix sg shpchp mptsas mptscsih mptbase scsi_transport_sas sd_mod crc_t10dif ext! 3! > j! >> bd mbcache >> >> >> Pid: 0, comm: swapper Tainted: G W 2.6.39-300.32.1.el5uek #1 Dell Inc. PowerEdge 2950/0DP246 >> RIP: e030:[] [] memcpy+0xb/0x120 >> RSP: e02b:ffff8801003c3d58 EFLAGS: 00010246 >> RAX: ffff880076b9e280 RBX: ffff8800714d2c00 RCX: 0000000000000057 >> RDX: 0000000000000000 RSI: ffff88006d9e8d48 RDI: ffff880076b9e280 >> RBP: ffff8801003c3dc0 R08: 00000000000bf723 R09: 0000000000000000 >> R10: 0000000000000000 R11: 000000000000000a R12: 0000000000000034 >> R13: 0000000000000034 R14: 00000000000002b8 R15: 00000000000005a8 >> FS: 00007fc1e852a6e0(0000) GS:ffff8801003c0000(0000) knlGS:0000000000000000 >> CS: e033 DS: 002b ES: 002b CR0: 000000008005003b >> CR2: ffff88006d9e8d48 CR3: 000000006370b000 CR4: 0000000000002660 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 >> Process swapper (pid: 0, threadinfo ffff880077ac0000, task ffff880077abe240) >> Stack: >> ffffffff8142db21 0000000000000000 ffff880076b9e280 ffff8800637097f0 >> 000002ec00000000 00000000000002b8 ffff880077ac0000 0000000000000000 >> ffff8800637097f0 ffff880066c9a7c0 00000000fffffdb4 000000000000024c >> Call Trace: >> >> [] ? skb_copy_bits+0x1c1/0x2e0 >> [] skb_copy+0xf3/0x120 >> [] neigh_timer_handler+0x1ac/0x350 >> [] ? account_idle_ticks+0xe/0x10 >> [] ? neigh_alloc+0x180/0x180 >> [] call_timer_fn+0x4a/0x110 >> [] ? neigh_alloc+0x180/0x180 >> [] run_timer_softirq+0x13a/0x220 >> [] __do_softirq+0xb9/0x1d0 >> [] ? handle_percpu_irq+0x48/0x70 >> [] call_softirq+0x1c/0x30 >> [] do_softirq+0x65/0xa0 >> [] irq_exit+0xab/0xc0 >> [] xen_evtchn_do_upcall+0x35/0x50 >> [] xen_do_hypervisor_callback+0x1e/0x30 >> >> [] ? xen_hypercall_sched_op+0xa/0x20 >> [] ? xen_hypercall_sched_op+0xa/0x20 >> [] ? xen_safe_halt+0x10/0x20 >> [] ? default_idle+0x5b/0x170 >> [] ? cpu_idle+0xc6/0xf0 >> [] ? xen_irq_enable_direct_reloc+0x4/0x4 >> [] ? cpu_bringup_and_idle+0xe/0x10 >> Code: 01 c6 43 4c 04 19 c0 4c 8b 65 f0 4c 8b 6d f8 83 e0 fc 83 c0 08 88 43 4d 48 8b 5d e8 c9 c3 90 90 48 89 f8 89 d1 c1 e9 03 83 e2 07 48 a5 89 d1 f3 a4 c3 20 48 83 ea 20 4c 8b 06 4c 8b 4e 08 4c >> RIP [] memcpy+0xb/0x120 >> RSP >> CR2: ffff88006d9e8d48 >> >> Reviewed vmcore I found the skb->users is 1 at the moment, checked network neighbour >> history I found skb_get() be replaced by skb_copy by commit 7e36763b2c: >> >> commit 7e36763b2c204d59de4e88087f84a2c0c8421f25 >> Author: Frank Blaschka >> Date: Mon Mar 3 12:16:04 2008 -0800 >> >> [NET]: Fix race in generic address resolution. >> >> neigh_update sends skb from neigh->arp_queue while neigh_timer_handler >> has increased skbs refcount and calls solicit with the >> skb. neigh_timer_handler should not increase skbs refcount but make a >> copy of the skb and do solicit with the copy. >> >> Signed-off-by: Frank Blaschka >> Signed-off-by: David S. Miller >> >> So can you please give some details of the race? per vmcore seems like the skb data >> be freed, I suspected skb_get() lost at somewhere? >> I reverted above commit the panic not occurred during our testing. >> >> Any input will appreciate! > > Well, fact is that your crash is happening in skb_copy(). > > Frank patch is OK. I suspect using skb_clone() would work too, > so if these skb were fclone ready, chance of an GFP_ATOMIC allocation > error would be smaller. > > So something is providing a wrong skb at the very beginning. > > You could try to do a early skb_copy to catch the bug and see in the > stack trace what produced this buggy skb. > > diff --git a/net/core/neighbour.c b/net/core/neighbour.c > index 5c56b21..a7a51fd 100644 > --- a/net/core/neighbour.c > +++ b/net/core/neighbour.c > @@ -1010,6 +1010,7 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb) > NEIGH_CACHE_STAT_INC(neigh->tbl, unres_discards); > } > skb_dst_force(skb); > + kfree_skb(skb_copy(skb, GFP_ATOMIC)); > __skb_queue_tail(&neigh->arp_queue, skb); > neigh->arp_queue_len_bytes += skb->truesize; > } > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/