kern/56189: System panicked: /: bad dir ino 5045785 at offset 0: Bad dir (too big)

[nia%pkgsrc.org@localhost]

>Number:         56189
>Category:       kern
>Synopsis:       System panicked: /: bad dir ino 5045785 at offset 0: Bad dir (too big)
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 19 10:20:00 +0000 2021
>Originator:     nia
>Release:        current
>Organization:
The NetBSD Foundation
>Environment:
NetBSD amnesia 9.99.82 NetBSD 9.99.82 (NIAAMD64) #2: Tue May 18 12:32:39 CEST 2021  nia@amnesia:/src/obj/sys/arch/amd64/compile/NIAAMD64 amd64
>Description:
System panicked: /: bad dir ino 5045785 at offset 0: Bad dir (too big), reclen=0x4918, namlen=61, dirsiz=72 <= reclen=18712 <= maxsize=512, flags=0x46005000, entryoffsetinblock=0, dirblksiz=512

Backtrace:

(gdb) target kvm /var/crash/netbsd.12.core
0xffffffff80230d05 in cpu_reboot (howto=howto@entry=260, 
    bootstr=bootstr@entry=0x0) at /src/src/sys/arch/amd64/amd64/machdep.c:713
713                     dumpsys();
(gdb) bt
#0  0xffffffff80230d05 in cpu_reboot (howto=howto@entry=260, 
    bootstr=bootstr@entry=0x0) at /src/src/sys/arch/amd64/amd64/machdep.c:713
#1  0xffffffff8297279c in kern_reboot (howto=howto@entry=260, 
    bootstr=bootstr@entry=0x0) at /src/src/sys/kern/kern_reboot.c:73
#2  0xffffffff82a6dd19 in vpanic (
    fmt=0xffffffff835c07d0 "%s: bad dir ino %ju at offset %d: %s\n", 
    ap=ap@entry=0xffffb180bd6709e8) at /src/src/sys/kern/subr_prf.c:290
#3  0xffffffff82a6df32 in panic (fmt=<optimized out>)
    at /src/src/sys/kern/subr_prf.c:209
#4  0xffffffff827bb404 in ufs_dirbad (how=<optimized out>, 
    offset=<optimized out>, ip=0xfffffd89281e2838)
    at /src/src/sys/ufs/ufs/ufs_lookup.c:750
#5  ufs_lookup (v=<optimized out>) at /src/src/sys/ufs/ufs/ufs_lookup.c:530
#6  0xffffffff82c0657a in VOP_LOOKUP (dvp=dvp@entry=0xfffffd8928d90100, 
    vpp=vpp@entry=0xffffb180bd670c28, cnp=cnp@entry=0xffffb180bd670e88)
    at /src/src/sys/kern/vnode_if.c:177
#7  0xffffffff82b9d5b8 in lookup_once (state=state@entry=0xffffb180bd670dd0, 
    searchdir=<optimized out>, 
    newsearchdir_ret=newsearchdir_ret@entry=0xffffb180bd670d20, 
    foundobj_ret=foundobj_ret@entry=0xffffb180bd670d28, 
    newsearchdir_locked_ret=newsearchdir_locked_ret@entry=0xffffb180bd670d1f)
    at /src/src/sys/kern/vfs_lookup.c:1179
#8  0xffffffff82ba055d in namei_oneroot (isnfsd=0, inhibitmagic=0, 
    neverfollow=0, state=0xffffb180bd670dd0)
    at /src/src/sys/kern/vfs_lookup.c:1587
#9  namei_tryemulroot (state=state@entry=0xffffb180bd670dd0, 
    neverfollow=neverfollow@entry=0, inhibitmagic=inhibitmagic@entry=0, 
--Type <RET> for more, q to quit, c to continue without paging--

fstab:

NAME=028ec817-9e7b-4862-8ffd-bf50f88b9594       /       ffs     rw,log,noatime,nodevmtime        1 1
NAME=c2f516b8-77d9-4d7c-88f0-6019113a30c4       none    swap    sw,dp    0 0
NAME=src        /src            ffs     rw,noatime,nosuid,nodev,log      1 2
tmpfs           /tmp            tmpfs   rw,noatime,nosuid,nodev,-m1777,-sram%25
kernfs          /kern           kernfs  rw
ptyfs           /dev/pts        ptyfs   rw,noatime
procfs          /proc           procfs  rw
tmpfs           /var/shm        tmpfs   rw,noatime,nosuid,nodev,-m1777,-sram%25
>How-To-Repeat:
Unknown. Happened on boot when mounting FFS filesystems, then went away
on reboot.
>Fix: