kern/53783: kernel panics. Possibly related to procfs.

[s-yamaguchi%iij.ad.jp@localhost]

>Number:         53783
>Category:       kern
>Synopsis:       kernel panics. Possibly related to procfs.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Dec 13 06:45:00 +0000 2018
>Originator:     Shoichi Yamaguchi
>Release:        8.0
>Organization:
IIJ
>Environment:
NetBSD netbsd8 8.0_STABLE NetBSD 8.0_STABLE (GENERIC) #0: Sat Dec  8 12:27:57 UTC 2018  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
The NetBSD-8 kernel panics when using htop(1) and procfs.
And the panic is happened in the NetBSD-7 kernel, too.

netbsd8# fatal protection fault in supervisor mode
trap type 4 code 0 rip 0xffffffff80960f36 cs 0x8 rflags 0x10286 cr2 0xffff8000342a3a4d ilevel 0 rsp 0xffff800032efe880
curlwp 0xfffffe8024538140 pid 12803.1 lowest kstack 0xffff800032efc2c0
panic: trap
cpu0: Begin traceback...
vpanic() at netbsd:vpanic+0x15d
snprintf() at netbsd:snprintf
trap() at netbsd:trap+0xa00
--- trap (number 4) ---
rw_oncpu.part.0() at netbsd:rw_oncpu.part.0+0x11
rw_vector_enter() at netbsd:rw_vector_enter+0x1bf
procfs_do_pid_stat() at netbsd:procfs_do_pid_stat+0xb5
procfs_rw() at netbsd:procfs_rw+0x301
VOP_READ() at netbsd:VOP_READ+0x50
vn_read() at netbsd:vn_read+0x94
dofileread() at netbsd:dofileread+0xa8
sys_read() at netbsd:sys_read+0x5f
syscall() at netbsd:syscall+0x1ec
--- syscall (number 3) ---
7afc0443e22a:
cpu0: End traceback...
rebooting...
>How-To-Repeat:
I was running the following three commands in the same time. And, after a few hours, the panic was caused.

commands:
shell-1$ htop -d 1 

shell-2$ while true; do find /proc > /dev/null 2>&1; done

shell-3$ while true; do sh -c "exit 0"; done
>Fix:
I don't know.