Hi Anand, Thanks for reporting this bug.
Could you please try the kernel version in xenial-proposed? [1] (version: 4.4.0-185.215) It has a patch for what seems to be this problem, according to the stack trace seen in apport's kernel crash dump below. The patch is: 'net: handle no dst on skb in icmp6_send' [1] https://wiki.ubuntu.com/Testing/EnableProposed cheers, Mauricio ... The stacktrace from apport's 'kernel crash dump' attachment (linux-image-4.4.0-184-generic-202006151751.crash): $ apport-unpack linux-image-4.4.0-184-generic-202006151751.crash k/ $ ls k Architecture Date DistroRelease Package ProblemType Uname VmCoreDmesg $ cat k/VmCoreDmesg ... [ 13.702003] nf_conntrack version 0.5.0 (16384 buckets, 65536 max) [ 962.936170] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 [ 962.936250] IP: [<ffffffff818288ab>] icmp6_send+0x1fb/0x970 [ 962.936296] PGD 0 [ 962.936314] Oops: 0000 [#1] SMP [ 962.936341] Modules linked in: xt_tcpudp nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter ip_tables x_tables vmw_vsock_vmci_transport vsock coretemp ppdev vmw_balloon input_leds joydev serio_raw shpchp vmw_vmci i2c_piix4 8250_fintek parport_pc mac_hid lp parport autofs4 xfs libcrc32c vmwgfx psmouse ttm drm_kms_helper syscopyarea sysfillrect mptspi sysimgblt mptscsih fb_sys_fops mptbase drm vmxnet3 scsi_transport_spi pata_acpi floppy fjes [ 962.936723] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.4.0-184-generic #214-Ubuntu [ 962.936775] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 09/17/2015 [ 962.936844] task: ffff88013a562700 ti: ffff88013a570000 task.ti: ffff88013a570000 [ 962.936893] RIP: 0010:[<ffffffff818288ab>] [<ffffffff818288ab>] icmp6_send+0x1fb/0x970 [ 962.936950] RSP: 0018:ffff88013fd83d00 EFLAGS: 00010246 [ 962.936986] RAX: 0000000000000000 RBX: ffff880139f88a00 RCX: 0000000000000020 [ 962.937032] RDX: 0000000000000001 RSI: 0000000000000200 RDI: ffff8800b8448fd6 [ 962.937079] RBP: ffff88013fd83e20 R08: 0000000000000000 R09: ffff8800b8448fe6 [ 962.937126] R10: 0000000000000080 R11: 0000000000000000 R12: ffff8800b8448fce [ 962.937172] R13: ffffffff81efb6c0 R14: 0000000000000001 R15: 0000000000000003 [ 962.937219] FS: 0000000000000000(0000) GS:ffff88013fd80000(0000) knlGS:0000000000000000 [ 962.937272] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 962.937310] CR2: 0000000000000018 CR3: 00000000ba602000 CR4: 0000000000000670 [ 962.937429] Stack: [ 962.937448] 0000000000000000 0000000000000000 000000e032fd4a6a ffff88010026d82b [ 962.937505] ffffffff810baaea ffff88013fd963b0 0000000000000000 ffff8800b8448fd6 [ 962.937565] ffff880100000001 0000000000000000 ffff8800b8448fe6 ffffffff810c077a [ 962.937623] Call Trace: [ 962.937642] <IRQ> [ 962.937664] [<ffffffff810baaea>] ? select_idle_sibling+0x2a/0x120 [ 962.937708] [<ffffffff810c077a>] ? enqueue_task_fair+0xaa/0x8b0 [ 962.937753] [<ffffffff81038119>] ? sched_clock+0x9/0x10 [ 962.937790] [<ffffffff810b8c8f>] ? sched_clock_cpu+0x8f/0xa0 [ 962.937832] [<ffffffff810b2524>] ? check_preempt_curr+0x54/0x90 [ 962.939091] [<ffffffff81868280>] ? _raw_spin_unlock_bh+0x20/0x50 [ 962.940307] [<ffffffff81841ed1>] icmpv6_send+0x21/0x30 [ 962.941522] [<ffffffff8182fe95>] ip6_expire_frag_queue+0x115/0x1b0 [ 962.942710] [<ffffffff8182ff30>] ? ip6_expire_frag_queue+0x1b0/0x1b0 [ 962.943892] [<ffffffff8182ff4f>] ip6_frag_expire+0x1f/0x30 [ 962.945057] [<ffffffff810f57c7>] call_timer_fn+0x37/0x140 [ 962.946241] [<ffffffff8182ff30>] ? ip6_expire_frag_queue+0x1b0/0x1b0 [ 962.947410] [<ffffffff810f70d4>] run_timer_softirq+0x234/0x330 [ 962.948537] [<ffffffff8108b509>] __do_softirq+0x109/0x2b0 [ 962.949638] [<ffffffff8108b825>] irq_exit+0xa5/0xb0 [ 962.950696] [<ffffffff8186c250>] smp_apic_timer_interrupt+0x50/0x70 [ 962.951734] [<ffffffff81869994>] apic_timer_interrupt+0xd4/0xe0 [ 962.952755] <EOI> [ 962.952775] [<ffffffff81039130>] ? speculation_ctrl_update_tif+0x80/0x80 [ 962.954720] [<ffffffff81067af2>] ? native_safe_halt+0x12/0x20 [ 962.955703] [<ffffffff8103914e>] default_idle+0x1e/0xe0 [ 962.956652] [<ffffffff81039ff5>] arch_cpu_idle+0x15/0x20 [ 962.957571] [<ffffffff810cc03a>] default_idle_call+0x2a/0x40 [ 962.958491] [<ffffffff810cc3b3>] cpu_startup_entry+0x303/0x360 [ 962.959399] [<ffffffff81053e67>] start_secondary+0x177/0x1b0 [ 962.960305] Code: 8b 5c 24 40 75 46 f6 c2 02 74 05 f6 c2 30 75 3c 48 8b 43 58 44 89 5c 24 34 89 54 24 40 44 89 44 24 48 4c 89 4c 24 60 48 83 e0 fe <48> 8b 78 18 e8 4c 0b 03 00 41 89 c2 4c 8b 4c 24 60 44 8b 44 24 [ 962.963319] RIP [<ffffffff818288ab>] icmp6_send+0x1fb/0x970 [ 962.964291] RSP <ffff88013fd83d00> [ 962.965247] CR2: 0000000000000018 -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1883681 Title: System freezes on specific kernel Status in linux package in Ubuntu: Confirmed Bug description: The servers will be running fine for some time and suddenly will freeze. It won't even respond to ping requests. We have to reboot the servers again to bring it back online but it won't be stable and will not respond again. --- AlsaDevices: total 0 crw-rw---- 1 root audio 116, 1 Jun 15 17:52 seq crw-rw---- 1 root audio 116, 33 Jun 15 17:52 timer AplayDevices: Error: [Errno 2] No such file or directory ApportVersion: 2.20.1-0ubuntu2.23 Architecture: amd64 ArecordDevices: Error: [Errno 2] No such file or directory AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1: DistroRelease: Ubuntu 16.04 HibernationDevice: RESUME=UUID=fe587596-cd68-4bbf-ae67-0e501fd6159c IwConfig: lo no wireless extensions. ens160 no wireless extensions. Lsusb: Error: command ['lsusb'] failed with exit code 1: MachineType: VMware, Inc. VMware Virtual Platform Package: linux (not installed) PciMultimedia: ProcEnviron: TERM=screen PATH=(custom, no user) LANG=en_US SHELL=/bin/bash ProcFB: 0 svgadrmfb ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-184-generic root=/dev/mapper/cdns01--vg-root ro crashkernel=384M-:128M ProcVersionSignature: Ubuntu 4.4.0-184.214-generic 4.4.223 RelatedPackageVersions: linux-restricted-modules-4.4.0-184-generic N/A linux-backports-modules-4.4.0-184-generic N/A linux-firmware 1.157.23 RfKill: Error: [Errno 2] No such file or directory Tags: xenial Uname: Linux 4.4.0-184-generic x86_64 UpgradeStatus: Upgraded to xenial on 2017-05-15 (1127 days ago) UserGroups: _MarkForUpload: True dmi.bios.date: 09/17/2015 dmi.bios.vendor: Phoenix Technologies LTD dmi.bios.version: 6.00 dmi.board.name: 440BX Desktop Reference Platform dmi.board.vendor: Intel Corporation dmi.board.version: None dmi.chassis.asset.tag: No Asset Tag dmi.chassis.type: 1 dmi.chassis.vendor: No Enclosure dmi.chassis.version: N/A dmi.modalias: dmi:bvnPhoenixTechnologiesLTD:bvr6.00:bd09/17/2015:svnVMware,Inc.:pnVMwareVirtualPlatform:pvrNone:rvnIntelCorporation:rn440BXDesktopReferencePlatform:rvrNone:cvnNoEnclosure:ct1:cvrN/A: dmi.product.name: VMware Virtual Platform dmi.product.version: None dmi.sys.vendor: VMware, Inc. 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