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While running an Ubuntu kernel (not a mainline or third-party kernel)
please enter the following command in a terminal window:

apport-collect 1728771

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable
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This change has been made by an automated script, maintained by the
Ubuntu Kernel Team.

** Changed in: linux (Ubuntu)
       Status: New => Incomplete

** Tags added: xenial

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https://bugs.launchpad.net/bugs/1728771

Title:
  BUG: unable to handle kernel NULL pointer dereference at
  0000000000000030

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  Trying to 'cat' a file in an overlayfs. The file is in the lowerdir. I
  use the attached script to create directories and randomly distributed
  files. $HOME is ecryptfs. /tmp/ is tmpfs.

  $ pwd
  $HOME/Hacking/overlayfs/

  $ ./build.sh

  $ sudo mount -t overlay overlay -o
  lowerdir=lower/1,upperdir=/tmp/upper/1,workdir=/tmp/workdir/1
  overlay/1

  $ grep /tmp /proc/mounts
  tmpfs /tmp tmpfs rw,nosuid,nodev,relatime 0 0
  overlay /home/tj/Hacking/overlayfs/overlay/1 overlay 
rw,relatime,lowerdir=lower/1,upperdir=/tmp/upper/1,workdir=/tmp/workdir/1 0 0

  $ ls lower/1/
  1b  1c  1d  1e  1f  1g  1k  1l  1o  1p  1q  1t  1u  1v  1w  1x  1y  1z

  $ ls /tmp/upper/1/
  1e  1i  1l  1n  1u

  $ ls overlay/1/
  1b  1c  1d  1e  1f  1g  1i  1k  1l  1n  1o  1p  1q  1t  1u  1v  1w  1x  1y  1z

  $ cat overlay/1/1b
  Killed

  $ uname -r
  4.13.0-16-lowlatency

  $ lsb_release -a
  LSB Version:    
core-9.20160110ubuntu0.2-amd64:core-9.20160110ubuntu0.2-noarch:security-9.20160110ubuntu0.2-amd64:security-9.20160110ubuntu0.2-noarch
  Distributor ID: Ubuntu
  Description:    Ubuntu 16.04.3 LTS
  Release:        16.04
  Codename:       xenial

  $ apt list linux-lowlatency-hwe-16.04-edge
  Listing... Done
  linux-lowlatency-hwe-16.04-edge/xenial-proposed,now 4.13.0.16.23 amd64 
[installed]

  $ tail /var/log/kern.log

  Oct 31 03:11:09 hephaestion kernel: [ 1057.380604] BUG: unable to handle 
kernel NULL pointer dereference at 0000000000000030
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380668] IP: 
ecryptfs_privileged_open+0x51/0x180
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380686] PGD 20ee07067
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380688] P4D 20ee07067
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380700] PUD 20c455067
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380711] PMD 0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380721]
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380741] Oops: 0000 [#1] PREEMPT SMP
  Oct 31 03:11:09 hephaestion kernel: [ 1057.380755] Modules linked in: overlay 
hidp scsi_transport_iscsi veth ip6t_MASQUERADE nf_nat_masquerade_ipv6 
ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 xt_comment 
xt_CHECKSUM iptable_mangle ipt_MASQUERADE nf_nat_masquerade_ipv4 iptable_nat 
nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 ccm xt_conntrack 
nf_conntrack ipt_REJECT nf_reject_ipv4 xt_tcpudp bridge ebtable_filter ebtables 
ip6table_filter ip6_tables iptable_filter ip_tables x_tables 8021q garp mrp stp 
llc rfcomm bnep binfmt_misc dm_thin_pool dm_persistent_data dm_bio_prison 
dm_bufio cdc_mbim cdc_wdm cdc_ncm usbnet cdc_acm mii gpio_ich dell_laptop 
coretemp btusb btrtl btbcm btintel joydev dell_wmi bluetooth dell_smbios dcdbas 
wmi_bmof sparse_keymap serio_raw ecdh_generic arc4 snd_hda_codec_idt 
snd_hda_codec_generic snd_hda_intel
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381004]  snd_hda_codec 
snd_hda_core input_leds snd_hwdep snd_pcm snd_seq_midi uvcvideo 
snd_seq_midi_event videobuf2_vmalloc videobuf2_memops snd_rawmidi 
videobuf2_v4l2 iwl4965 videobuf2_core iwlegacy videodev media mac80211 snd_seq 
r852 sm_common nand nand_ecc nand_bch bch mtd r592 memstick lpc_ich cfg80211 
snd_seq_device snd_timer snd soundcore shpchp mac_hid kvm_intel kvm irqbypass 
parport_pc ppdev nfsd lp auth_rpcgss nfs_acl lockd grace parport sunrpc autofs4 
crypto_simd glue_helper cryptd aes_x86_64 algif_skcipher af_alg dm_crypt raid10 
raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq 
libcrc32c raid1 raid0 multipath linear dm_mirror dm_region_hash dm_log 
hid_generic usbhid hid psmouse sky2 ahci nouveau libahci pata_acpi 
firewire_ohci sdhci_pci sdhci firewire_core
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  crc_itu_t mxm_wmi 
i2c_algo_bit video ttm drm_kms_helper syscopyarea sysfillrect sysimgblt 
fb_sys_fops drm wmi
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] CPU: 0 PID: 10087 Comm: 
cat Tainted: P           OE   4.13.0-16-lowlatency #19~16.04.3-Ubuntu
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] Hardware name: Dell Inc. 
XPS M1530                       /      , BIOS A12 11/19/2008
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] task: ffff8a1167050000 
task.stack: ffffa10c010a8000
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RIP: 
0010:ecryptfs_privileged_open+0x51/0x180
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RSP: 0018:ffffa10c010abb60 
EFLAGS: 00010246
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RAX: ffffa10c010abb88 RBX: 
ffff8a1167459540 RCX: ffff8a11677ced80
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RDX: ffffffffbeefbe60 RSI: 
ffffffffbe6999fb RDI: ffffa10c010abb80
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RBP: ffffa10c010abbd0 R08: 
ffffffffbdd68aa1 R09: ffff8a118a183800
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] R10: ffff8a113175d010 R11: 
ffff8a113175e278 R12: 0000000000000000
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] R13: ffff8a11677ced80 R14: 
0000000000000000 R15: ffff8a11cd431710
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] FS:  
00007f80f7700700(0000) GS:ffff8a11dfc00000(0000) knlGS:0000000000000000
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] CS:  0010 DS: 0000 ES: 
0000 CR0: 0000000080050033
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] CR2: 0000000000000030 CR3: 
000000020d763000 CR4: 00000000000006f0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] Call Trace:
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  
ecryptfs_get_lower_file+0x7d/0xc0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ecryptfs_open+0x71/0x200
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  do_dentry_open+0x1f8/0x320
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? 
ecryptfs_release+0x30/0x30
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  vfs_open+0x4e/0x80
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  path_openat+0x2a8/0x13c0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? 
unlock_page_memcg+0x12/0x20
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? 
page_add_file_rmap+0x58/0x170
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  do_filp_open+0x99/0x110
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? cp_new_stat+0x156/0x190
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? 
__check_object_size+0xfc/0x1a0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? __alloc_fd+0xae/0x170
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  do_sys_open+0x12d/0x2a0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  ? do_sys_open+0x12d/0x2a0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  SyS_open+0x1e/0x20
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012]  
entry_SYSCALL_64_fastpath+0x1e/0xa9
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RIP: 0033:0x7f80f7245010
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RSP: 002b:00007fff0583f8d8 
EFLAGS: 00000246 ORIG_RAX: 0000000000000002
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RAX: ffffffffffffffda RBX: 
00007fff0583fb38 RCX: 00007f80f7245010
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RDX: 0000000000020000 RSI: 
0000000000000000 RDI: 00007fff05840237
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RBP: 0000000000001000 R08: 
0000000000000000 R09: 0000000000000000
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] R10: 000000000000069d R11: 
0000000000000246 R12: 00000000004025b0
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] R13: 00007fff0583fb30 R14: 
0000000000000000 R15: 0000000000000000
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] Code: c2 60 be ef be 49 89 
cd 65 48 8b 04 25 28 00 00 00 48 89 45 d8 31 c0 48 8d 45 90 c7 45 a8 00 00 00 
00 48 8d 78 20 e8 1f 91 d5 ff <49> 8b 44 24 30 48 89 5d 90 4c 89 65 a0 4c 89 75 
98 48 8b 40 28
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] RIP: 
ecryptfs_privileged_open+0x51/0x180 RSP: ffffa10c010abb60
  Oct 31 03:11:09 hephaestion kernel: [ 1057.381012] CR2: 0000000000000030
  Oct 31 03:11:09 hephaestion kernel: [ 1057.391461] ---[ end trace 
1d38ad38c6419426 ]---

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