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[Bug 1490267] Re: Regression in overlayfs


I observe a repeatable crash on Wily; when the system is rebooted, the
callstack in the crash report is similar to the one in comment #13
("BUG: unable to handle kernel NULL pointer dereference", dput -
ovl_rename2 - vfs_rename - ...).

The crash is triggered by the usage of an unprivileged LXC container
with overlayfs storage.

It rarely happens on kernel 4.2.0-22, much more frequently with kernel
4.2.0-23,  very reliably with 4.2.0-25. Also it seems that replacing
system RAM with a faster one increased the incidence of the crash.

Unlike Thomas's case in #15, my system locks up completely (only Ctrl-
Alt-Shift-SysRq-B works).

I hope I'm not off topic here; my kernel is different from the one in
the original report but the stack trace is similar so I think it might
be the same root cause. I'll be glad to provide any additional info or
perform experiments.

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  Regression in overlayfs

Status in linux package in Ubuntu:

Bug description:
  When installing the linux-lts-vivid kernel in Ubuntu 14.04, there is a
  regression with overlayfs and unprivileged containers: 'failed to

  Below the system information:

  - Kernel error: http://pastebin.com/iajXHbHZ
  - Kernel version: 3.19.0-25-generic #26~14.04.1-Ubuntu SMP Fri Jul 24 21:16:20 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
  - Executed LXC command: lxc-clone -s -B overlayfs orig test (both unprivileged containers)
  - LXC version: 1.0.7

  We discussed this on the LXC user mailing list, and this is likely a bug in one of the patches that add support for unprivileged use of overlayfs.
   total 0
   crw-rw---- 1 root audio 116,  1 Aug 30 13:56 seq
   crw-rw---- 1 root audio 116, 33 Aug 30 13:56 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.14.1-0ubuntu3.12
  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 14.04
  Ec2AMI: ami-fceee9e1
  Ec2AMIManifest: (unknown)
  Ec2AvailabilityZone: eu-central-1b
  Ec2InstanceType: t2.micro
  Ec2Kernel: unavailable
  Ec2Ramdisk: unavailable
  IwConfig: Error: [Errno 2] No such file or directory
  Lsusb: Error: command ['lsusb'] failed with exit code 1: unable to initialize libusb: -99
  MachineType: Xen HVM domU
  Package: linux (not installed)
   PATH=(custom, no user)
   0 cirrusdrmfb
   1 xen
  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-26-generic root=UUID=dde0e30e-be54-43dc-9a44-5769353c2e27 ro console=tty1 console=ttyS0
  ProcVersionSignature: Ubuntu 3.19.0-26.28~14.04.1-generic 3.19.8-ckt4
   linux-restricted-modules-3.19.0-26-generic N/A
   linux-backports-modules-3.19.0-26-generic  N/A
   linux-firmware                             1.127.15
  RfKill: Error: [Errno 2] No such file or directory
  StagingDrivers: visorutil
  Tags:  trusty ec2-images staging
  Uname: Linux 3.19.0-26-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  _MarkForUpload: True
  dmi.bios.date: 05/06/2015
  dmi.bios.vendor: Xen
  dmi.bios.version: 4.2.amazon
  dmi.chassis.type: 1
  dmi.chassis.vendor: Xen
  dmi.modalias: dmi:bvnXen:bvr4.2.amazon:bd05/06/2015:svnXen:pnHVMdomU:pvr4.2.amazon:cvnXen:ct1:cvr:
  dmi.product.name: HVM domU
  dmi.product.version: 4.2.amazon
  dmi.sys.vendor: Xen

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