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[Launchpad Bug Tracker <1807077@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package mountall - 2.53ubuntu1

---------------
mountall (2.53ubuntu1) trusty; urgency=medium

  * try_udev_device: Ignore udev block device nodes which are missing
    devnames (LP: #1807077).

 -- Ryan Finnie <ryan.finnie@xxxxxxxxxxxxx>  Thu, 06 Dec 2018 03:29:27
+0000

** Changed in: mountall (Ubuntu Trusty)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1807077

Title:
  [SRU] mountall crashes on udev node with missing devname

Status in mountall package in Ubuntu:
  Invalid
Status in mountall source package in Trusty:
  Fix Released
Status in mountall source package in Xenial:
  Won't Fix

Bug description:
  [Impact]

   * udev block nodes without a devname will crash mountall, resulting
  in an unbootable system (emergency root shell)

   * While this is not likely to happen in a matched distro/kernel
  environment (it was discovered while needing to run a bionic 4.15
  kernel on trusty), it is possible.

   * The code in try_udev_device() assumes a block subsystem will always
  have a devname; the SRU patches explicitly check for a devname and
  return if null.

  [Test Case]

   * HPE DL385 Gen10, Samsung a822 NVMe controller, trusty install

   * Kernels <4.15 (or possibly 4.14) do not expose nvme0c33n1 and do
  not trigger the bug.  Tested on 4.13, 4.4 and 3.13.

   * Kernel 4.15 exposes nvme0c33n1 in udev but does not have a devname,
  mountall crash ensues.

  [Regression Potential]

   * Patch might ignore legitimate block devices on existing
  installations.  Unlikely, since the logic path for null devname leads
  directly to a program crash.

  [Other Info]

   * Additional context for Canonical employees: PS4.5 is a trusty
  backend cloud, but we now have Gen10 hardware incoming (this was
  discovered while adding new nova-compute hardware).  Older kernels are
  not usable because Gen10 requires ilorest, which requires a >4.4
  kernel (at least artful 4.13 is known good).  So trusty+4.15 is the
  only viable combination for continued support of the cloud while
  adding new hardware.  This is done via apt pinning of bionic for the
  kernel packages, and, mountall notwithstanding, is working fine so
  far.

  TEST CASE:
  1. Enable -proposed
  2. apt-get install mountall=2.53ubuntu1
  3. update-initramfs -k all -u
  4. Reboot

  VERIFICATION DONE
  Rebooted successfully on affected Gen10 systems.  Confirmed no regression on unaffected systems.

  
  Original description:

  Running bionic's 4.15 kernel on trusty on an HPE DL385 Gen10 results
  in a device node for the NVMe controller,
  /devices/pci0000:40/0000:40:03.1/0000:43:00.0/nvme/nvme0/nvme0c33n1
  which itself does not have a devname.  When mountall gets to it:

  fsck_update: updating check priorities
  try_mount: /srv/nova/instances waiting for device
  try_udev_device: ignored /dev/loop5 (not yet ready?)
  try_udev_device: ignored /dev/loop6 (not yet ready?)
  try_udev_device: ignored /dev/loop1 (not yet ready?)
  try_udev_device: ignored /dev/loop0 (not yet ready?)
  try_udev_device: block (null) (null) (null)

  and then crashes, leaving the boot at an emergency root shell.  A
  successful scan looks like this for comparison:

  try_udev_device: block /dev/sdb (null) (null)
  try_udev_device: block /dev/sdb (null) (null)
  try_udev_device: block /dev/sda (null) (null)
  try_udev_device: block /dev/nvme0n1 ed56e3a9-60f7-4636-85a2-b53137b598e7 (null)
  try_udev_device: block /dev/bcache0 756cb2c6-b999-4905-a021-c2e688e81a86 instances

  The debdiffs check for a null devname in try_udev_device() and will
  not attempt to process it.

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