panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/main/kernel/sys/kern/kern_synch.c", line 944
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:437
panic(ffffffff83405dd0) at panic+0x1cf sys/kern/subr_prf.c:198
__assert(ffffffff833b3398,ffffffff83301e66,3b0,ffffffff833bb56d) at __assert+0x29
refcnt_finalize(ffff80002a8eb5d8,ffffffff833033a1) at refcnt_finalize+0x1c8 sys/kern/kern_synch.c:945
pppx_if_destroy(205b92,ffff80002a8eb5d0) at pppx_if_destroy+0x3d sys/net/if_pppx.c:806
pppxclose(205b92,1,2000,ffff80002a8c8d08) at pppxclose+0xa0 sys/net/if_pppx.c:553
spec_close(ffff80002a7ff2e0) at spec_close+0x412
VOP_CLOSE(fffffd8063cae0d8,1,fffffd807f7d77b8,ffff80002a8c8d08) at VOP_CLOSE+0x12a sys/kern/vfs_vops.c:156
vn_closefile(fffffd806c5569e8,ffff80002a8c8d08) at vn_closefile+0x11d vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd806c5569e8,ffff80002a8c8d08) at vn_closefile+0x11d sys/kern/vfs_vnops.c:615
fdrop(fffffd806c5569e8,ffff80002a8c8d08) at fdrop+0x126 sys/kern/kern_descrip.c:1265
closef(fffffd806c5569e8,ffff80002a8c8d08) at closef+0x18d sys/kern/kern_descrip.c:1249
fdfree(ffff80002a8c8d08) at fdfree+0x115 sys/kern/kern_descrip.c:1181
exit1(ffff80002a8c8d08,0,0,1) at exit1+0x57f sys/kern/kern_exit.c:214
sys_exit(ffff80002a8c8d08,ffff80002a7ff650,ffff80002a7ff5a0) at sys_exit+0x1a
end trace frame: 0xffff80002a7ff640, count: 0
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