panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 944
Starting stack trace...
panic(ffffffff8343b582) at panic+0x1d0 sys/kern/subr_prf.c:229
__assert(ffffffff833e7d34,ffffffff833f04dc,3b0,ffffffff833f0524) at __assert+0x29
refcnt_finalize(ffff80003c5d3990,ffffffff8332fc97) at refcnt_finalize+0x1c8 sys/kern/kern_synch.c:945
pppx_if_destroy(205b9a,ffff80003c5d3988) at pppx_if_destroy+0x3d sys/net/if_pppx.c:806
pppxclose(205b9a,1,2000,ffff8000ffff6a58) at pppxclose+0xa0 sys/net/if_pppx.c:553
spec_close(ffff800033cb7ee0) at spec_close+0x412
VOP_CLOSE(fffffd805f895988,1,fffffd807f7d3410,ffff8000ffff6a58) at VOP_CLOSE+0x133 sys/kern/vfs_vops.c:156
vn_closefile(fffffd806adc6e58,ffff8000ffff6a58) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd806adc6e58,ffff8000ffff6a58) at vn_closefile+0x12b sys/kern/vfs_vnops.c:615
fdrop(fffffd806adc6e58,ffff8000ffff6a58) at fdrop+0x126 sys/kern/kern_descrip.c:1265
closef(fffffd806adc6e58,ffff8000ffff6a58) at closef+0x192 sys/kern/kern_descrip.c:1249
fdfree(ffff8000ffff6a58) at fdfree+0x116 sys/kern/kern_descrip.c:1181
exit1(ffff8000ffff6a58,0,0,1) at exit1+0x57f sys/kern/kern_exit.c:214
sys_exit(ffff8000ffff6a58,ffff800033cb8250,ffff800033cb81a0) at sys_exit+0x1a
syscall(ffff800033cb8250) at syscall+0xb08 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff800033cb8250) at syscall+0xb08 sys/arch/amd64/amd64/trap.c:577
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x6f8eba922980, count: 242
End of stack trace.