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[Michael Hudson-Doyle <michael.hudson+lp@xxxxxxxxxxxxx>]

** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Also affects: snap-confine (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** No longer affects: linux (Ubuntu Xenial)

** Changed in: snap-confine (Ubuntu Xenial)
       Status: New => In Progress

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https://bugs.launchpad.net/bugs/1584456

Title:
  apparmor denial using ptmx char device

Status in Snappy Launcher:
  Fix Released
Status in linux package in Ubuntu:
  Confirmed
Status in snap-confine package in Ubuntu:
  Fix Released
Status in snap-confine source package in Xenial:
  In Progress

Bug description:
  [Impact]

  snap-confine would refuse to work on an older kernel running on an
  Nvidia Tegra X1 board. This was traced to a bug in older version of
  apparmor there that required directory-like syntax for /dev/pts/ptmx
  (with a trailing slash).

  This bug is fixed by adding an apparmor rule, identical to the normal
  rule, with an extra slash. Older kernels will use the new rule while
  current kernels will just ignore it.

  [Test Case]

  On an Nvidia Tegra X1 board, running 3.10.96 snap-confine should no
  longer fail to start. On Ubuntu Xenial (all architectures) there
  should be no perceived change.

  Snap-confine is carefully tested with a battery of spread tests that
  can be found here: https://github.com/snapcore/snap-
  confine/blob/master/spread-tests/

  The test cases are ran automatically for each pull request and for
  each final release.

  All those tests were executed successfully for this release. As a
  simple test case consider running any snap (any at all, including
  hello-world).

  [Regression Potential]

   * Regression potential is minimal as the fix simply adds another
  apparmor rule that grants additional permissions that are only picked
  up by old buggy kernels.

  * The fix was tested on Ubuntu via spread.

  [Other Info]

  * This bug is a part of a major SRU that brings snap-confine in Ubuntu
  16.04 in line with the current upstream release 1.0.41.

  * This bug was included in an earlier SRU and is now fixed in Ubuntu.
  I am updating the template here to ensure that the process is fully
  documented from 1.0.38 all the way up to the current upstream release
  1.0.41.

  * snap-confine is technically an integral part of snapd which has an
  SRU exception and is allowed to introduce new features and take
  advantage of accelerated procedure. For more information see
  https://wiki.ubuntu.com/SnapdUpdates

  == # Pre-SRU bug description follows # ==

  - Finding issues running snaps (hello-world).
  - Same issue even installing with --devmode. Even running the snap binary as root
  - Using a custom kernel, this is on an Nvidia Tegra X1 custom board.

  =====================================

  ubuntu@localhost:~$ hello-world.echo plop
  unable to mount '/dev/pts/ptmx'->'/dev/ptmx'. errmsg: Permission denied
  ubuntu@localhost:~$ sudo hello-world.echo plop
  unable to mount '/dev/pts/ptmx'->'/dev/ptmx'. errmsg: Permission denied

  dmesg shows:
  =====================================

  [  302.838046] type=1400 audit(1455208371.989:16): apparmor="DENIED"
  operation="mount" info="failed mntpnt match" error=-13 parent=911
  profile="/usr/bin/ubuntu-core-launcher" name="/dev/ptmx/" pid=912
  comm="ubuntu-core-lau" srcname="/dev/pts/ptmx/" flags="rw, bind"
  [  308.080449] type=1400 audit(1455208377.229:17): apparmor="DENIED"
  operation="mount" info="failed mntpnt match" error=-13 parent=914
  profile="/usr/bin/ubuntu-core-launcher" name="/dev/ptmx/" pid=915
  comm="ubuntu-core-lau" srcname="/dev/pts/ptmx/" flags="rw, bind"

  This is with the "hello-world" snap installed with "snap install"

  Output of an ls over the device file:
  =====================================

  ubuntu@localhost:~$ ls -lR /dev/ptmx /dev/pts
  crw-rw-rw- 1 root tty  5, 2 Feb 11 16:28 /dev/ptmx

  /dev/pts:
  total 0
  c--------- 1 root root 5, 2 Jan  1  1970 ptmx

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