Public bug reported:

== SRU Justification Focal ==

zfs mount -a when run on a nonempty mountpoint causes a double free,
memory corruption, and a segfault.

== Impact ==

Double free and memory corruption in ZFS when run as root and attempting
to mount all. While running this I observed other ZFS volumes randomly
unmounting, and mount points owner being spuriously zeroed (set to
root).

== Fix ==

https://github.com/openzfs/zfs/commit/d1b84da8c1a69c084f04b504beefe804591bca07

== Test ==

Steps are laid out in the ZFS issue:
https://github.com/openzfs/zfs/issues/9560

== Regression Potential ==

Limited to the behavior of zfs mount when a previous attempt to mount
has failed, or is still in progress. Changes the behavior in that case
to failure, instead of double-free.


Example case of running into this bug, with dmesg:
https://pastebin.com/YRXW8WgM

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.1 LTS
Release:        20.04
Codename:       focal


$ apt-cache policy zfsutils-linux
zfsutils-linux:
  Installed: 0.8.3-1ubuntu12.4
  Candidate: 0.8.3-1ubuntu12.4
  Version table:
 *** 0.8.3-1ubuntu12.4 500
        500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 
Packages
        100 /var/lib/dpkg/status
     0.8.3-1ubuntu12 500
        500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages

** Affects: zfs-linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1902588

Title:
  zfs mount -a: double free / memory corruption / segfault when
  mountpoint of dataset is not empty

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