[lxc-users] kernel crash when starting an unprivileged container

[Tomasz Chmielewski]

It may be worth trying, but it won't work reliably for most kernel 
crashes (network, disk IO etc. may crash as well).

-- 
Tomasz Chmielewski
http://wpkg.org

On 2015-06-10 14:11, Christoph Lehmann wrote:
> As a side note, you can use rsyslogs remotelogging to get the oops
> 
> Am 3. Juni 2015 08:01:22 MESZ, schrieb Tomasz Chmielewski
> <mangoo at wpkg.org>:
> 
>> I'm trying to start an unprivileged container on Ubuntu 14.04;
>> unfortunately, the kernel crashes.
>> 
>> # lxc-create -t download -n test-container
>> (...)
>> Distribution: ubuntu
>> Release: trusty
>> Architecture: amd64
>> (...)
>> 
>> # lxc-start -n test-container -F
>> 
>> Kernel crashes at this point.
>> 
>> It does not crash if I start the container as privileged.
>> 
>> - kernel used is 4.0.4-040004-generic from
>> http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0.4-wily [1]/
>> 
>> - lxc userspace: http://ppa.launchpad.net/ubuntu-lxc/stable/ubuntu
>> [2]
>> 
>> # dpkg -l|grep lxc
>> ii liblxc1
>> 1.1.2-0ubuntu3~ubuntu14.04.1~ppa1 amd64 Linux Containers
>> userspace tools (library)
>> ii lxc !
>> 
>> 1.1.2-0ubuntu3~ubuntu14.04.1~ppa1 amd64 Linux Containers
>> userspace tools
>> ii lxc-templates
>> 1.1.2-0ubuntu3~ubuntu14.04.1~ppa1 amd64 Linux Containers
>> userspace tools (templates)
>> ii lxcfs
>> 0.7-0ubuntu4~ubuntu14.04.1~ppa1 amd64 FUSE based filesystem
>> for LXC
>> ii python3-lxc
>> 1.1.2-0ubuntu3~ubuntu14.04.1~ppa1 amd64 Linux Containers
>> userspace tools (Python 3.x bindings)
>> 
>> It's a bit hard to get the printout of the OOPS, as I'm only able to
>> 
>> access the server remotely and it doesn't manage to write the OOPS
>> to
>> the log.
>> 
>> Anyway, after a few crashes and "while true; do dmesg -c ; done" I
>> was
>> able to capture this:
>> 
>> [ 237.706914] device vethPI4H7F entered promiscuous mode
>> [ 237.707006] IPv6: ADDRCONF(NETDEV_UP): vethPI4H7F:!
>> link is
>> not ready
>> [ 237.797284] eth0: renamed from veth1OSOTS
>> [ 237.824526] IPv6: ADDRCONF(NETDEV_CHANGE): vethPI4H7F: link
>> becomes
>> ready
>> [ 237.824556] lxcbr0: port 1(vethPI4H7F) entered forwarding state
>> [ 237.824562] lxcbr0: port 1(vethPI4H7F) entered forwarding state
>> [ 237.928179] BUG: unable to handle kernel NULL pointer dereference
>> at
>> (null)
>> [ 237.928262] IP: [<ffffffff8122f888>] pin_remove+0x58/0xf0
>> [ 237.928318] PGD 0
>> [ 237.928364] Oops: 0002 [#1] SMP
>> [ 237.928432] Modules linked in: xt_conntrack veth xt_CHECKSUM
>> iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat
>> nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack
>> xt_tcpudp iptable_filter ip_tables x_tables bridge stp llc
>> intel_rapl
>> iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel
>> kvm
>> crct10dif_pclmul crc32_pclmul eeepc_wmi ghash_clmulni_intel
>> aesni_intel
>> asus_wmi
>> sparse_keymap ie31200_edac aes_x86_64 edac_core lrw gf128mul
>> glue_helper shpchp lpc_ich ablk_helper cryptd mac_hid 8250_fintek
>> serio_raw tpm_infineon video wmi btrfs lp parport raid10 raid456
>> async_raid6_recov async_memcpy async_pq async_xor async_tx xor
>> raid6_pq
>> e1000e raid1 ahci raid0 ptp libahci pps_core multipath linear
>> [ 237.930151] CPU: 2 PID: 6568 Comm: lxc-start Not tainted
>> 4.0.4-040004-generic #201505171336
>> [ 237.930188] Hardware name: System manufacturer System Product
>> Name/P8B WS, BIOS 0904 10/24/2011
>> [ 237.930225] task: ffff880806970a00 ti: ffff8808090c8000 task.ti:
>> ffff8808090c8000
>> [ 237.930259] RIP: 0010:[<ffffffff8122f888>] [<ffffffff8122f888>]
>> pin_remove+0x58/0xf0
>> [ 237.930341] RSP: 0018:ffff8808090cbe18 EFLAGS: 00010246
>> [ 237.930383] RAX: 0000000000000000 RBX: ffff880808808a20 RCX:
>> dead000000100100
>> [ 237.930429] RDX: 0000000000000000 RSI: dead0000002!
>> 00200
>> RDI:
>> ffffffff81f9a548
>> [ 237.930474] RBP: ffff8808090cbe28 R08: ffffffff81d11b60 R09:
>> 0000000000000100
>> [ 237.930572] R13: ffff880806970a00 R14: ffffffff81ecd070 R15:
>> 00007ffe57fd5540
>> [ 237.930618] FS: 00007fd4aaaa48c0(0000) GS:ffff88082fa80000(0000)
>> knlGS:0000000000000000
>> [ 237.930685] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 237.930728] CR2: 0000000000000000 CR3: 00000008099c1000 CR4:
>> 00000000000407e0
>> [ 237.930773] Stack:
>> [ 237.930809] ffff880806970a00 ffff880808808a20 ffff8808090cbe48
>> ffffffff8121d0f2
>> [ 237.930957] ffff8808090cbe68 ffff880808808a20 ffff8808090cbea8
>> ffffffff8122fa55
>> [ 237.931123] 0000000000000000 ffff880806970a00 ffffffff810bb2b0
>> ffff8808090cbe70
>> [ 237.931286] Call Trace:
>> [ 237.931336] [<ffffffff8121d0f2>] drop_mountpoint+0x22/0x40
>> [ 237.931380] [<ffffffff8122fa55>] pin_kill+0x75/0x130
>> [ 237.931425]
>> [<ffffffff810bb2b0>] ? prepare_to_wait_event+0x100/0x100
>> [ 237.931471] [<ffffffff8122fb39>] mnt_pin_kill+0x29/0x40
>> [ 237.931530] [<ffffffff8121baf0>] cleanup_mnt+0x80/0x90
>> [ 237.931573] [<ffffffff8121bb52>] __cleanup_mnt+0x12/0x20
>> [ 237.931617] [<ffffffff81096ad7>] task_work_run+0xb7/0xf0
>> [ 237.931662] [<ffffffff8101607c>] do_notify_resume+0xbc/0xd0
>> [ 237.931709] [<ffffffff817f0beb>] int_signal+0x12/0x17
> 
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