panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/main/kernel/sys/kern/kern_synch.c", line 951
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(ffffffff83432fbe) at panic+0x1cf sys/kern/subr_prf.c:198
__assert(ffffffff833e0581,ffffffff833288fe,3b7,ffffffff833e1660) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80002a8b6b60,ffffffff8332acdc) at refcnt_finalize+0x1c8 sys/kern/kern_synch.c:952
pppx_if_destroy(205b9a,ffff80002a8b6b58) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794
pppxclose(205b9a,1,2000,ffff80002a79a038) at pppxclose+0xa0 sys/net/if_pppx.c:541
spec_close(ffff80003c96d120) at spec_close+0x412 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffd80690191d0,1,fffffd8007bfb8f0,ffff80002a79a038) at VOP_CLOSE+0x12a sys/kern/vfs_vops.c:156
vn_closefile(fffffd805eef2258,ffff80002a79a038) at vn_closefile+0x11d vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd805eef2258,ffff80002a79a038) at vn_closefile+0x11d sys/kern/vfs_vnops.c:615
fdrop(fffffd805eef2258,ffff80002a79a038) at fdrop+0x126 sys/kern/kern_descrip.c:1267
closef(fffffd805eef2258,ffff80002a79a038) at closef+0x18d sys/kern/kern_descrip.c:1251
fdfree(ffff80002a79a038) at fdfree+0x115 sys/kern/kern_descrip.c:1182
exit1(ffff80002a79a038,0,0,1) at exit1+0x59c sys/kern/kern_exit.c:215
sys_exit(ffff80002a79a038,ffff80003c96d490,ffff80003c96d3e0) at sys_exit+0x1a sys/kern/kern_exit.c:-1
end trace frame: 0xffff80003c96d480, count: 0
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