kern/55602: zpool panic on mounting zfs filesystem

[abs%absd.org@localhost]

>Number:         55602
>Category:       kern
>Synopsis:       zpool panic on mounting zfs filesystem
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 23 23:05:00 +0000 2020
>Originator:     David Brownlee
>Release:        NetBSD 9.0_STABLE
>Organization:
	
>Environment:
System: NetBSD iris.absd.org 9.0_STABLE NetBSD 9.0_STABLE (GENERIC) #0: Thu Aug 20 16:16:33 UTC 2020 mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
Architecture: x86_64
Machine: amd64
>Description:

System panics on mounting a zpool - whether as part of "zpool create" 
or "zpool import"

Specifying a different mount point "zpool create -m /var/obj test /dev/wd0"
does not help.

No panic occurs if the system is booted to single user, "mount /" is run 
and then "zpool create test /dev/wd0".

The panic _does_ occur if the system is booted to multi user, then shutdown
to single user, "umount -va" is run and then "zpool create test /dev/wd0"

A 9.99.71 kernel & modules from nyftp via the "boot to multiuser then
shutdown before testing" also panics

Sample stacktrace (from 9)

vpanic() at netbsd:vpanic+0x160
snprintf() at netbsd:snprintf
startlwp() at netbsd:startlwp
alltraps() at netbsd:alltraps+0xbb
fstrans_start() at netbsd:fstrans_start+0x64
VOP_LOCK() at netbsd:VOP_LOCK+0x52
vn_lock() at netbsd:vn_lock+0x11
secmodel_extension_system_cb() at netbsd:secmodel_extensions_system_cb+0x70
kauth_authorize_action() at netbsd:kauth_authorize_action+0xa?
kauth_authorize_system() at netbsd:kauth_authorize_system+0x2?
zfs_mount() at zfs:zfs_mount+0xcf
VFS_MOUNT() at netbsd:VFS_MOUNT+0x4d
mount_domount() at netbsd:mount_domount+0xdf
do_sys_mount() at netbsd:do_sys_mount+0x580  

>How-To-Repeat:
zpool create test /dev/wd0
>Fix: