assert "(pg->pg_flags & PG_BUSY) == NUM" failed in pmap.c

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 456e8b6ad58e ftp: send 'Accept */*' header
git tree: openbsd
console output: https://syzkaller.appspot.com/x/log.txt?x=118baeab180000
kernel config: https://syzkaller.appspot.com/x/.config?x=1bc15e68cd2a49e5
dashboard link: https://syzkaller.appspot.com/bug?extid=90b9aac60da3a5360280

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/547db3a390d0/disk-456e8b6a.raw.xz
bsd.gdb: https://storage.googleapis.com/syzbot-assets/d4325dffaa76/bsd-456e8b6a.gdb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3a5e6a464ba7/kernel-456e8b6a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+90b9aa...@syzkaller.appspotmail.com

panic: kernel diagnostic assertion "(pg->pg_flags & PG_BUSY) == 0" failed: file "/syzkaller/managers/main/kernel/sys/arch/amd64/amd64/pmap.c", line 1422
Starting stack trace...
panic(ffffffff82929e0e) at panic+0x159 sys/kern/subr_prf.c:229
__assert(ffffffff828e1086,ffffffff82838776,58e,ffffffff8288f167) at __assert+0x29 sys/kern/subr_prf.c:157
pmap_destroy(fffffd8077ce8d90) at pmap_destroy+0x2a4 sys/arch/amd64/amd64/pmap.c:1422
uvm_map_teardown(fffffd806826b988) at uvm_map_teardown+0x287 sys/uvm/uvm_map.c:2557
uvmspace_free(fffffd806826b988) at uvmspace_free+0x96 sys/uvm/uvm_map.c:3461
vm_teardown(ffff80002d930ec0) at vm_teardown+0x105 sys/dev/vmm/vmm.c:555
vm_terminate(ffff80002d931160) at vm_terminate+0x121 sys/dev/vmm/vmm.c:688
vmmioctl(a00,80045604,ffff80002d931160,1,ffff80002a62b208) at vmmioctl+0x291 sys/dev/vmm/vmm.c:248
VOP_IOCTL(fffffd806e7cb1b0,80045604,ffff80002d931160,1,fffffd807f7d7750,ffff80002a62b208) at VOP_IOCTL+0x91 sys/kern/vfs_vops.c:264
vn_ioctl(fffffd80618ad2d8,80045604,ffff80002d931160,ffff80002a62b208) at vn_ioctl+0xbb sys/kern/vfs_vnops.c:525
sys_ioctl(ffff80002a62b208,ffff80002d931340,ffff80002d931290) at sys_ioctl+0x4a5
syscall(ffff80002d931340) at syscall+0x72a sys/arch/amd64/amd64/trap.c:577
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x839f615b560, count: 244
End of stack trace.
syncing disks...10 4 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 giving up

dump to dev 4,1 not possible
rebooting...
SeaBIOS (version 1.8.2-google)
Total RAM Size = 0x0000000080000000 = 2048 MiB
CPUs found: 2 Max CPUs supported: 2
SeaBIOS (version 1.8.2-google)
Machine UUID 860ebdd0-427f-2be6-5726-fd56b385017a
found virtio-scsi at 0:3
virtio-scsi vendor='Google' product='PersistentDisk' rev='1' type=0 removable=0
virtio-scsi blksize=512 sectors=4194304 = 2048 MiB
drive 0x000f27f0: PCHS=0/0/0 translation=lba LCHS=520/128/63 s=4194304
Sending Seabios boot VM event.
Booting from Hard Disk 0...
>> OpenBSD/amd64 BOOT 3.65
boot> machine ddbcpu 0
machine: syntax error
boot> trace
| / - \ | / - \ | / booting hd0a:trace: - \ | / open hd0a:trace: No such file or directory
failed(2). will try /bsd
boot> machine ddbcpu 1
machine: syntax error
boot> trace


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