Date:	Tue, 28 Sep 2010 02:18:42 +0400
From:	Michael Tokarev <mjt@....msk.ru>
To:	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, kvm-devel <kvm@...r.kernel.org>
Subject: Re: [stable 2.6.32] instant crash (jump to NULL) with virtio-net,
 tap, bridge and veth

Replying to my own, quite old (more than a month old)
email, and top-posting as well.

I had a chance finally to try another theory with this
problem -- the suspect this time was stack overflow.
And indeed it looks like the case.  I can disable
the bridge hooks in /proc/sys/net/bridge/, and the
system works just fine (in the backtraces we can
see ip_rcv_finish() and ip_rcv() calls, which are
in the NF_HOOK macro).

So, by disabling all nf hooks the problem goes away.
After enabling them again the kernel crashes again
as before.

Since this is our production host, I wont do more
tests in a near future, leaving the nf hooks disabled.

Thanks for listening!

/mjt

25.08.2010 19:50, Michael Tokarev wrote:
> Hello.
> 
> I'm seeing instant host kernel crash triggered by _any_
> network activity to/from a kvm guest that's using virtio-net.
> 
> My setup is maybe a bit unusual, but here we go.
> 
> I've a host machine that has one bridge configured,
> and is running a few kvm virtual machines and a few
> linux containers (LXC).  All the guests/containers
> are "connected" to that single bridge - guests using
> tap devices, lxc containers using veth devices. Host
> eth0 is connected to the same bridge as well.
> 
> The problem happens with virtio-net drivers used in
> guest (this is windowsXP virtual machine with latest
> netkvm driver from alt.fedoraproject.org), when I
> connect to that guest from an LXC container.  I.e,
> when packet goes lxc => veth => bridge => tun =>
> kvm => virtio in guest (or back).
> 
> When I connect to the same guest from _host_, it all
> works as expected.  When I change (virtual) NIC in
> guest to e1000 or older (from 2009) virtio-net driver,
> it works.  When I connect from lxc container to a
> linux guest with latest virtio-net drivers, it all
> works as expected too.  So only one combination so
> far that triggers the issue.
> 
> This is all with 2.6.32 kernel.  Initially it was
> 2.6.32.15, but 2.6.32.20 behaves the same way too.
> All 64bit.
> 
> Also it does NOT happen with 2.6.35.3, the current
> latest released kernel.
> 
> Here's one of captured OOPSes (i did it several
> times, but they were incomplete):
> 
> console [netcon0] enabled
> netconsole: network logging started
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<(null)>] (null)
> PGD 177bf2067 PUD 177ae5067 PMD 0
> Oops: 0010 [#1] SMP
> last sysfs file: /sys/devices/virtual/block/md8/md/mismatch_cnt
> CPU 0
> Modules linked in: netconsole configfs squashfs kvm_amd kvm veth autofs4 bridge quota_v2 quota_tree ext4 jbd2 crc16 raid0 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx loop sr_mod cdrom tun powernow_k8 processor thermal_sys 8021q garp stp llc asus_atk0110 hwmon atl1 mii ext3 jbd mbcache raid1 md_mod pata_atiixp ehci_hcd ohci_hcd usbcore nls_base ahci libata sd_mod scsi_mod
> Pid: 2345, comm: kvm Not tainted 2.6.32-amd64 #2.6.32.20 System Product Name
> RIP: 0010:[<0000000000000000>]  [<(null)>] (null)
> RSP: 0018:ffff880028203e70  EFLAGS: 00010293
> RAX: ffff880179480ec0 RBX: ffff8801a07770c0 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffff8801a07770c0 RDI: ffff8801a07770c0
> RBP: ffff880124b89030 R08: ffffffff8125fab0 R09: ffff880028203e40
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff880028210888
> R13: ffff880028210880 R14: 000000010000e60f R15: 0000000000000040
> FS:  00007fe2da5e5700(0000) GS:ffff880028200000(0000) knlGS:00000000f74a59d0
> CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> CR2: 0000000000000000 CR3: 0000000177a8a000 CR4: 00000000000006f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
> Process kvm64 (pid: 2345, threadinfo ffff880177be2000, task ffff880177a7c0c0)
> Stack:
>  ffffffff8125fbd5 0000000000000040 ffffffff8126013c 0000000080000000
> <0> ffff8800282108b8 0000000000000002 ffff880028210888 ffff880028210880
> <0> ffffffff81236276 ffff880028203f48 ffff8800282108b8 0000000000000000
> Call Trace:
>  <IRQ>
>  [<ffffffff8125fbd5>] ? ip_rcv_finish+0x125/0x430
>  [<ffffffff8126013c>] ? ip_rcv+0x25c/0x350
>  [<ffffffff81236276>] ? process_backlog+0x76/0xd0
>  [<ffffffff81236a18>] ? net_rx_action+0xf8/0x1f0
>  [<ffffffff81059120>] ? __do_softirq+0xb0/0x1d0
>  [<ffffffff8100c56c>] ? call_softirq+0x1c/0x30
>  <EOI>
>  [<ffffffff8100e595>] ? do_softirq+0x65/0xa0
>  [<ffffffff81236b2e>] ? netif_rx_ni+0x1e/0x30
>  [<ffffffffa014e97a>] ? tun_chr_aio_write+0x35a/0x510 [tun]
>  [<ffffffffa014e620>] ? tun_chr_aio_write+0x0/0x510 [tun]
>  [<ffffffff810ffea4>] ? do_sync_readv_writev+0xd4/0x110
>  [<ffffffff8106e890>] ? autoremove_wake_function+0x0/0x30
>  [<ffffffff81071709>] ? enqueue_hrtimer+0x79/0xc0
>  [<ffffffff810ffd08>] ? rw_copy_check_uvector+0x88/0x110
>  [<ffffffff811005bc>] ? do_readv_writev+0xdc/0x220
>  [<ffffffff8106dafc>] ? sys_timer_settime+0x13c/0x2e0
>  [<ffffffff8110084e>] ? sys_writev+0x4e/0x90
>  [<ffffffff8100b482>] ? system_call_fastpath+0x16/0x1b
> Code:  Bad RIP value.
> RIP  [<(null)>] (null)
>  RSP <ffff880028203e70>
> CR2: 0000000000000000
> ---[ end trace 1dcd3c52bde0fa25 ]---
> Kernel panic - not syncing: Fatal exception in interrupt
> Pid: 2345, comm: kvm Tainted: G      D    2.6.32-amd64 #2.6.32.20
> Call Trace:
>  <IRQ>  [<ffffffff812c22de>] ? panic+0x7a/0x134
>  [<ffffffff812c23d8>] ? printk+0x40/0x48
>  [<ffffffff8100faa3>] ? oops_end+0xa3/0xb0
>  [<ffffffff8103138a>] ? no_context+0xfa/0x260
>  [<ffffffff812c52a5>] ? page_fault+0x25/0x30
>  [<ffffffff8125fab0>] ? ip_rcv_finish+0x0/0x430
>  [<ffffffff8125fbd5>] ? ip_rcv_finish+0x125/0x430
>  [<ffffffff8126013c>] ? ip_rcv+0x25c/0x350
>  [<ffffffff81236276>] ? process_backlog+0x76/0xd0
>  [<ffffffff81236a18>] ? net_rx_action+0xf8/0x1f0
>  [<ffffffff81059120>] ? __do_softirq+0xb0/0x1d0
>  [<ffffffff8100c56c>] ? call_softirq+0x1c/0x30
>  <EOI>  [<ffffffff8100e595>] ? do_softirq+0x65/0xa0
>  [<ffffffff81236b2e>] ? netif_rx_ni+0x1e/0x30
>  [<ffffffffa014e97a>] ? tun_chr_aio_write+0x35a/0x510 [tun]
>  [<ffffffffa014e620>] ? tun_chr_aio_write+0x0/0x510 [tun]
>  [<ffffffff810ffea4>] ? do_sync_readv_writev+0xd4/0x110
>  [<ffffffff8106e890>] ? autoremove_wake_function+0x0/0x30
>  [<ffffffff81071709>] ? enqueue_hrtimer+0x79/0xc0
>  [<ffffffff810ffd08>] ? rw_copy_check_uvector+0x88/0x110
>  [<ffffffff811005bc>] ? do_readv_writev+0xdc/0x220
>  [<ffffffff8106dafc>] ? sys_timer_settime+0x13c/0x2e0
>  [<ffffffff8110084e>] ? sys_writev+0x4e/0x90
>  [<ffffffff8100b482>] ? system_call_fastpath+0x16/0x1b
> Rebooting in 60 seconds..
> 
> 
> Another:
> 
> BUG: unable to handle kernel NULL pointer dereference at (null)
> IP: [<(null)>] (null)
> PGD 10c804067 PUD 212d0e067 PMD 0
> Oops: 0010 [#1] SMP
> last sysfs file: /sys/devices/virtual/vc/vcsa2/dev
> CPU 0
> Modules linked in: netconsole configfs squashfs kvm_amd kvm veth autofs4 bridge quota_v2 quota_tree ext4 jbd2 crc16 raid0 raid456 async_pq async_xor xor async_memcpy async_raid6_recov raid6_pq async_tx loop sr_mod cdrom tun powernow_k8 processor thermal_sys 8021q garp stp llc asus_atk0110 hwmon atl1 mii ext3 jbd mbcache raid1 md_mod pata_atiixp ehci_hcd ohci_hcd usbcore nls_base [<ffffffff8100bff3>] ? apic_timer_interrupt+0x13/0x20
>  [<ffffffff8100fced>] ? oops_end+0x9d/0xb0
>  [<ffffffff810320b7>] ? no_context+0xf7/0x260
>  [<ffffffff81032375>] ? __bad_area_nosemaphore+0x155/0x230
>  [<ffffffffa0273ea0>] ? br_nf_pre_routing_finish+0x0/0x350 [bridge]
>  [<ffffffffa0274759>] ? br_nf_pre_routing+0x569/0x880 [bridge]
>  [<ffffffff812cc945>] ? page_fault+0x25/0x30
>  [<ffffffff812650a0>] ? ip_rcv+0x0/0x350
>  [<ffffffff81264c60>] ? ip_rcv_finish+0x0/0x440
>  [<ffffffff81264e19>] ? ip_rcv_finish+0x1b9/0x440
>  [<ffffffff81265354>] ? ip_rcv+0x2b4/0x350
>  [<ffffffff8123ba85>] ? process_backlog+0x75/0xc0
>  [<ffffffff8123c246>] ? net_rx_action+0x106/0x220
>  [<ffffffff8105abcb>] ? __do_softirq+0xfb/0x1d0
>  [<ffffffff8100c62c>] ? call_softirq+0x1c/0x30
>  <EOI>  [<ffffffff8100e765>] ? do_softirq+0x65/0xa0
>  [<ffffffff8123c379>] ? netif_rx_ni+0x19/0x20
>  [<ffffffffa0151b0b>] ? tun_chr_aio_write+0x3fb/0x550 [tun]
>  [<ffffffffa0151710>] ? tun_chr_aio_write+0x0/0x550 [tun]
>  [<ffffffff811031fb>] ? do_sync_readv_writev+0xcb/0x110
>  [<ffffffff81065941>] ? __dequeue_signal+0xe1/0x210
>  [<ffffffff810706b0>] ? autoremove_wake_function+0x0/0x30
>  [<ffffffff81012bc2>] ? read_tsc+0x12/0x40
>  [<ffffffff81024608>] ? lapic_next_event+0x18/0x20
>  [<ffffffff8107d156>] ? tick_dev_program_event+0x36/0xb0
>  [<ffffffff81103036>] ? rw_copy_check_uvector+0x86/0x130
>  [<ffffffff81103912>] ? do_readv_writev+0xe2/0x230
>  [<ffffffff8106f883>] ? sys_timer_settime+0x153/0x350
>  [<ffffffff81103bb3>] ? sys_writev+0x53/0xa0
>  [<ffffffff8100b542>] ? system_call_fastpath+0x16/0x1b
> Rebooting in 60 seconds..
> 
> I looked at the changes in tun, virtio-net, bridge code and
> veth between 2.6.32 and 2.6.35, but I see nothing relevant
> in there (but I'm not an expert in that area anyway). The
> changes mentions a few crashes, but all were related to
> device registration/deregistration or module unload, not
> to normal send/receive path.
> 
> It will be really nice to fix this for long-stable 2.6.32
> series... ;)
> 
> Thanks!
> 
> /mjt
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