panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 953
Stopped at      db_enter+0x25:  addq    $0x8,%rsp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438
panic(ffffffff833962ae) at panic+0x1e5 sys/kern/subr_prf.c:198
__assert(ffffffff833d23e4,ffffffff833e3947,3b9,ffffffff8340d639) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80003c462350,ffffffff8338af85) at refcnt_finalize+0x1db sys/kern/kern_synch.c:954
pppx_if_destroy(0,ffff80003c462348) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794
pppxclose(285b9a,41,2000,ffff8000fffef4d8) at pppxclose+0xa0 sys/net/if_pppx.c:541
spec_close(ffff8000397f2c60) at spec_close+0x417 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffd806c12cb18,41,fffffd80097fb618,ffff8000fffef4d8) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156
vn_closefile(fffffd806a18b090,ffff8000fffef4d8) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd806a18b090,ffff8000fffef4d8) at vn_closefile+0x12b sys/kern/vfs_vnops.c:615
fdrop(fffffd806a18b090,ffff8000fffef4d8) at fdrop+0x121 sys/kern/kern_descrip.c:1280
closef(fffffd806a18b090,ffff8000fffef4d8) at closef+0x192 sys/kern/kern_descrip.c:1264
fdfree(ffff8000fffef4d8) at fdfree+0x116 sys/kern/kern_descrip.c:1195
exit1(ffff8000fffef4d8,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215
sys_exit(ffff8000fffef4d8,ffff8000397f2fd0,ffff8000397f2f20) at sys_exit+0x1a sys/kern/kern_exit.c:-1
end trace frame: 0xffff8000397f2fc0, count: 0
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