kern/54311: panic: kernel diagnostic assertion "!"kernel path too long in pathbuf_create"" failed

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54311
>Category:       kern
>Synopsis:       panic: kernel diagnostic assertion "!"kernel path too long in pathbuf_create"" failed
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Jun 19 18:35:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-currrent, source date 2019.06.18.23.53.55
>Organization:

>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

The test VMs on the TNF i386 testbed are failing to complete the tests
because the lib/libc/sys/t_mknod:mknod_err test case is triggering a
panic:

lib/libc/sys/t_mknod (290/801): 4 test cases
    mknod_err: [ 7935.4265244] panic: kernel diagnostic assertion "!"kernel path too long in pathbuf_create"" failed: file "/tmp/bracket/build/2019.06.18.23.53.55-i386/src/sys/kern/vfs_lookup.c", line 308
[ 7935.4265244] cpu0: Begin traceback...
[ 7935.4265244] vpanic(c10a7000,c9906dec,c9906e00,c09c2b66,c10a7000,c10a6f3f,c1175994,c117566c,134,c9906e3c) at netbsd:vpanic+0x12d
[ 7935.4465199] kern_assert(c10a7000,c10a6f3f,c1175994,c117566c,134,c9906e3c,c9906e10,c09c2bf4,bfb4f993,c23f30a0) at netbsd:kern_assert+0x23
[ 7935.4465199] pathbuf_create(bfb4f993,c23f30a0,c9906f14,c09d0a46,bfb4f993,1,c9906e3c,0,0,0) at netbsd:pathbuf_create+0x63
[ 7935.4465199] pathbuf_maybe_copyin(bfb4f993,1,c9906e3c,0,0,0,16,c1baf000,c23d6270,c1a65e08) at netbsd:pathbuf_maybe_copyin+0x1c
[ 7935.4665218] do_sys_mknodat(c23f30a0,ffffff9c,bfb4f993,2000,0,0,1,c9906f9c,c01589c1,c23f30a0) at netbsd:do_sys_mknodat+0x86
[ 7935.4665218] sys___mknod50(c23f30a0,c9906f68,c9906f60,c1b899e0,ffffffff,c9906f60,1c2,c9906f68,0,0) at netbsd:sys___mknod50+0x3f
[ 7935.4865231] syscall() at netbsd:syscall+0x151
[ 7935.4865231] --- syscall (number 450) ---
[ 7935.4865231] b8243357:
[ 7935.4865231] cpu0: End traceback...

[ 7935.4865231] dumping to dev 168,1 offset 1030
[ 7935.4865231] dump 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 succeeded

For the full console log, see the "tests: did not complete" link at

  http://releng.netbsd.org/b5reports/i386/commits-2019.06.html#2019.06.18.23.53.55

or one of the other similar links that will soon appear as more test
runs time out.

>How-To-Repeat:

Run the ATF tests.

>Fix: