panic: knote_enqueue:LINE: kq=ADDR kn=ADDR knote !QUEUED

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: eb4d0442 Use type M_KEVENT instead of M_TEMP when allocati..
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=11173e15e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=bf87b6915a88cd0d
dashboard link: https://syzkaller.appspot.com/bug?extid=6a1dfebcd03d6b31c80e

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6a1dfe...@syzkaller.appspotmail.com

panic: knote_enqueue:1276: kq=0xfffffd806e7c0d68 kn=0xfffffd806eb54380
knote !QUEUED
Stopped at db_enter+0x18: addq $0x8,%rsp
TID PID UID PRFLAGS PFLAGS CPU COMMAND
328176 50068 0 0 0 1 syz-executor.1
* 45585 50068 0 0 0x4000000 0K syz-executor.1
db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398
panic(ffffffff8220dc07) at panic+0x15c sys/kern/subr_prf.c:207
kqueue_do_check(fffffd806e7c0d68,ffffffff82251644,4fc) at
kqueue_do_check+0x232 sys/kern/kern_event.c:596
knote_enqueue(fffffd806eb54380) at knote_enqueue+0x80
sys/kern/kern_event.c:1277
kqueue_register(fffffd806e7c0d68,ffff800021bbafa0,ffff800020ac8780) at
kqueue_register+0x820 sys/kern/kern_event.c:769
sys_kevent(ffff800020ac8780,ffff800021bbb168,ffff800021bbb1b0) at
sys_kevent+0x2b6 sys/kern/kern_event.c:552
syscall(ffff800021bbb230) at syscall+0x4a4 mi_syscall
sys/sys/syscall_mi.h:92 [inline]
syscall(ffff800021bbb230) at syscall+0x4a4 sys/arch/amd64/amd64/trap.c:555
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xd4bcd63e900, count: 7
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports. Insufficient info makes it difficult to find and fix bugs.


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[Anton Lindqvist]

#syz dup: kqueue: knote !QUEUED