kern/55417: Creating many, many tap(4)'s panics the system

[jruohonen%iki.fi@localhost]

>Number:         55417
>Category:       kern
>Synopsis:       Creating many, many tap(4)'s panics the system
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 25 14:05:00 +0000 2020
>Originator:     jruohonen%iki.fi@localhost
>Release:        NetBSD 9.99.68
>Organization:
>Environment:
System: NetBSD kafka 9.99.68 NetBSD 9.99.68 (CUSTOM) #0: Tue Jun 23 11:22:56 EEST 2020 jruoho@kafka:/tmp/obj/sys/arch/amd64/compile/CUSTOM amd64
Architecture: x86_64
Machine: amd64
>Description:
The system panics either upon the creation or the deletion of a large number
of tap(4) devices.
>How-To-Repeat:
Create a huge number (i.e., thousands) of tap(4)'s sequentially, and then
destroy these sequentially. A hand-copied trace:

[...]
Stopped in pid 9053.9053 (ifconfig) at  netbsd:config_devalloc+0x112:   cmpq
$0,0(%rcx,%r15,8)
config_devalloc() at netbsd:config_devalloc+0x112
config_attach_pseudo at netbsd:config_attach_pseudo+0x16
tap_clone_creator() at netbsd:tap_clone_creator+0x46
tap_clone_create() at netbsd_tap_clone_create+0x12
doifioctl() at netbsd:doifioctl+0xe6e
[...]
>Fix:
N/A