group.of.nepali.translators team mailing list archive

[Mauricio Faria de Oliveira <mfo@xxxxxxxxxxxxx>]

Public bug reported:

The nilfs filesystem has a backup superblock at the end of the device.

If the magic number is coincidentally found at the right position
and the filesystem is on a partition/not-wholedisk device,
the only check left is for checksum verification,
which is explicitly ignored in 'udev built-in blkid'.

This causes blkid to detect one actually valid filesystem with a
superblock at the beginning of the device (e.g., ext4), and then
an invalid nilfs2 filesystem due to a coincidental magic number
at the end of the device.

And this causes blkid to break out of the safeprobe routine
(which expects a single filesystem to be detected), and not
print the UUIDs, thus not creating /dev/disk/by-uuid/ links
which prevent mounting the partition by-uuid at boot time,
causing emergency shell/boot failures.

This upstream fix resolved the problem by introducing a check
for the 'bytes' paramenters in the superblock, which is read
from disk, and turns out to have an out-of-range value.

- 'liblkid: Add length check in probe_nilfs2 before crc32'
https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=ac681a310c32319423297544833932f4d689a7a2

$ git describe --contains ac681a310c32319423297544833932f4d689a7a2
v2.29-rc1~172

Xenial, which is v2.27.1-based, is the only release that needs it.
Bionic is v2.31.1, so all post-Xenial supported releases have it.

** Affects: util-linux (Ubuntu)
     Importance: Undecided
         Status: Fix Released

** Affects: util-linux (Ubuntu Xenial)
     Importance: Medium
     Assignee: Mauricio Faria de Oliveira (mfo)
         Status: In Progress

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

** Changed in: util-linux (Ubuntu)
       Status: New => Fix Released

** Changed in: util-linux (Ubuntu Xenial)
       Status: New => In Progress

** Changed in: util-linux (Ubuntu Xenial)
     Assignee: (unassigned) => Mauricio Faria de Oliveira (mfo)

** Changed in: util-linux (Ubuntu Xenial)
   Importance: Undecided => Medium

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https://bugs.launchpad.net/bugs/1842437

Title:
  Xenial: libblkid: fix false-positive/misdetection of nilfs2 filesystem
  with udev

Status in util-linux package in Ubuntu:
  Fix Released
Status in util-linux source package in Xenial:
  In Progress

Bug description:
  The nilfs filesystem has a backup superblock at the end of the device.

  If the magic number is coincidentally found at the right position
  and the filesystem is on a partition/not-wholedisk device,
  the only check left is for checksum verification,
  which is explicitly ignored in 'udev built-in blkid'.

  This causes blkid to detect one actually valid filesystem with a
  superblock at the beginning of the device (e.g., ext4), and then
  an invalid nilfs2 filesystem due to a coincidental magic number
  at the end of the device.

  And this causes blkid to break out of the safeprobe routine
  (which expects a single filesystem to be detected), and not
  print the UUIDs, thus not creating /dev/disk/by-uuid/ links
  which prevent mounting the partition by-uuid at boot time,
  causing emergency shell/boot failures.

  This upstream fix resolved the problem by introducing a check
  for the 'bytes' paramenters in the superblock, which is read
  from disk, and turns out to have an out-of-range value.

  - 'liblkid: Add length check in probe_nilfs2 before crc32'
  https://git.kernel.org/pub/scm/utils/util-linux/util-linux.git/commit/?id=ac681a310c32319423297544833932f4d689a7a2

  $ git describe --contains ac681a310c32319423297544833932f4d689a7a2
  v2.29-rc1~172

  Xenial, which is v2.27.1-based, is the only release that needs it.
  Bionic is v2.31.1, so all post-Xenial supported releases have it.

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