Public bug reported: I don't know how to reproduce this, as it worked for 2 weeks before happening, but was consistent then.
I used btrfs on top of bcache on top of lvm. While trying to sbuild a package I got strange errors, got this messge in dmesg. Kernel 4.2.0-7-lowlatency release: wily: lsblk: NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 465,8G 0 disk ├─hdd-Work 252:4 0 232,9G 0 lvm │ └─bcache0 251:0 0 232,9G 0 disk /home └─hdd-Home 252:5 0 232,9G 0 lvm └─bcache1 251:1 0 232,9G 0 disk /media/Work sdb 8:16 0 238,5G 0 disk ├─sdb1 8:17 0 512M 0 part /boot/efi ├─sdb2 8:18 0 244M 0 part /boot └─sdb3 8:19 0 237,8G 0 part ├─ssd-root 252:0 0 64G 0 lvm / ├─ssd-bcache 252:1 0 64G 0 lvm │ ├─bcache0 251:0 0 232,9G 0 disk /home │ └─bcache1 251:1 0 232,9G 0 disk /media/Work ├─ssd-swap 252:2 0 8G 0 lvm │ └─cryptswap1 252:6 0 8G 0 crypt [SWAP] └─ssd-Free 252:3 0 101,8G 0 lvm /media/Free loop0 7:0 0 800M 0 loop └─secrets 252:7 0 798M 0 crypt /home/kick/Secrets Kernel traces: [ 224.670454] BUG: unable to handle kernel NULL pointer dereference at 0000000000000334 [ 224.672387] IP: [<ffffffffc0305601>] btrfs_sync_file+0xc1/0x360 [btrfs] [ 224.674261] PGD 8451a067 PUD 84527067 PMD 0 [ 224.676056] Oops: 0002 [#1] PREEMPT SMP [ 224.677810] Modules linked in: algif_skcipher af_alg ipt_REJECT nf_reject_ipv4 ebtable_filter ebtables ip6_tables overlay xt_addrtype xt_conntrack xt_CHECKSUM ax88179_178a iptable_mangle usbnet ipt_MASQUERADE rtsx_usb_ms nf_nat_masquerade_ipv4 aufs iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 mii memstick nf_nat_ipv4 nf_nat nf_conntrack xt_tcpudp bridge stp llc binfmt_misc iptable_filter ip_tables x_tables bnep drbg ansi_cprng dm_crypt nls_iso8859_1 intel_rapl iosf_mbi x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul snd_soc_rt5640 glue_helper ablk_helper snd_soc_rl6231 cryptd snd_soc_core input_leds serio_raw hid_sensor_rotation snd_compress ac97_bus snd_pcm_dmaengine snd_seq_midi snd_seq_midi_event snd_hda_codec_realtek [ 224.683606] hid_sensor_incl_3d uvcvideo videobuf2_vmalloc snd_hda_codec_generic hid_sensor_als videobuf2_memops hid_sensor_magn_3d snd_hda_codec_hdmi hid_sensor_accel_3d hid_sensor_gyro_3d btusb hid_sensor_trigger btrtl industrialio_triggered_buffer btbcm snd_rawmidi joydev btintel videobuf2_core kfifo_buf snd_hda_intel industrialio snd_hda_codec hid_sensor_iio_common v4l2_common videodev snd_hda_core hid_multitouch snd_hwdep media bluetooth mei_me snd_seq lpc_ich mei snd_pcm snd_seq_device dw_dmac dw_dmac_core snd_timer snd soundcore ideapad_laptop sparse_keymap 8250_dw i2c_designware_platform mac_hid spi_pxa2xx_platform soc_button_array i2c_designware_core snd_soc_sst_acpi kvm_intel kvm parport_pc ppdev lp parport autofs4 btrfs xor raid6_pq hid_sensor_custom hid_sensor_hub uas usb_storage bcache [ 224.689905] hid_generic usbhid rtsx_usb_sdmmc rtsx_usb i915 i2c_algo_bit drm_kms_helper drm psmouse ahci libahci sdhci_acpi sdhci video i2c_hid hid [ 224.694241] CPU: 1 PID: 2915 Comm: debconf-set-sel Tainted: G W 4.2.0-7-lowlatency #7-Ubuntu [ 224.696433] Hardware name: LENOVO 20344/INVALID, BIOS 96CN25WW(V1.11) 07/09/2014 [ 224.698641] task: ffff880099723800 ti: ffff880084510000 task.ti: ffff880084510000 [ 224.700843] RIP: 0010:[<ffffffffc0305601>] [<ffffffffc0305601>] btrfs_sync_file+0xc1/0x360 [btrfs] [ 224.703068] RSP: 0018:ffff880084513e38 EFLAGS: 00010292 [ 224.705272] RAX: ffff880099723800 RBX: ffff880159625400 RCX: 0000000000000000 [ 224.707505] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880098237a58 [ 224.709733] RBP: ffff880084513eb8 R08: 0000000000000001 R09: 0000000001f94ff0 [ 224.711962] R10: 000000000000009c R11: 0000000000000246 R12: ffff880098237a58 [ 224.714191] R13: ffff8800982379b0 R14: 0000000000000000 R15: 0000000000000000 [ 224.716431] FS: 00007fdffa459700(0000) GS:ffff88015f240000(0000) knlGS:0000000000000000 [ 224.718656] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 224.720882] CR2: 0000000000000334 CR3: 000000008456a000 CR4: 00000000001406e0 [ 224.723098] Stack: [ 224.725289] ffff880159625410 0000000200000001 8000000000000000 ffff8800981d7d80 [ 224.727494] 7fffffffffffffff 0000000000000000 0000000000000000 ffff88009a803000 [ 224.729686] 0000000000001144 0000000000000002 ffff880084513ea8 ffff880159625400 [ 224.731860] Call Trace: [ 224.733994] [<ffffffff8122468b>] vfs_fsync_range+0x4b/0xb0 [ 224.736142] [<ffffffff8122474d>] do_fsync+0x3d/0x70 [ 224.738275] [<ffffffff812249d0>] SyS_fsync+0x10/0x20 [ 224.740379] [<ffffffff817c4bf2>] entry_SYSCALL_64_fastpath+0x16/0x75 [ 224.742476] Code: eb a1 e8 37 da cf c0 eb 9a 48 8b 45 a0 4c 8b 75 a8 4d 8d a5 a8 00 00 00 4c 89 e7 4c 29 f0 48 83 c0 01 48 89 45 90 e8 0f d4 4b c1 <f0> 41 ff 87 34 03 00 00 49 8b 85 70 ff ff ff 48 c1 e8 07 83 e0 [ 224.744787] RIP [<ffffffffc0305601>] btrfs_sync_file+0xc1/0x360 [btrfs] [ 224.746956] RSP <ffff880084513e38> [ 224.749088] CR2: 0000000000000334 [ 224.751273] ---[ end trace 7e8588f0d9eb10fa ]--- ** Affects: linux (Ubuntu) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1496438 Title: 4.2.0.7 BUG: unable to handle kernel NULL pointer dereference at 0000000000000334 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1496438/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs