syzbot

panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/main/kernel/sys/kern/kern_synch.c", line 959
Starting stack trace...
panic(ffffffff83481619) at panic+0x1ba sys/kern/subr_prf.c:229
__assert(ffffffff834c2163,ffffffff83523175,3bf,ffffffff834fc545) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80002a7526c8,ffffffff8347f173) at refcnt_finalize+0x1e7 sys/kern/kern_synch.c:960
pppx_if_destroy(285b9a,ffff80002a7526c0) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794
pppxclose(285b9a,41,2000,ffff80002a766d08) at pppxclose+0xa0 sys/net/if_pppx.c:541
spec_close(ffff8000364bd3e0) at spec_close+0x417 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffb006fa7fc28,41,fffffb0007ffd410,ffff80002a766d08) at VOP_CLOSE+0x129 sys/kern/vfs_vops.c:156
vn_closefile(fffffb006d490880,ffff80002a766d08) at vn_closefile+0x11d vn_close sys/kern/vfs_vnops.c:298 [inline]
vn_closefile(fffffb006d490880,ffff80002a766d08) at vn_closefile+0x11d sys/kern/vfs_vnops.c:621
fdrop(fffffb006d490880,ffff80002a766d08) at fdrop+0x121 sys/kern/kern_descrip.c:1281
closef(fffffb006d490880,ffff80002a766d08) at closef+0x190 sys/kern/kern_descrip.c:1265
fdfree(ffff80002a766d08) at fdfree+0x115 sys/kern/kern_descrip.c:1196
exit1(ffff80002a766d08,b,0,1) at exit1+0x595 sys/kern/kern_exit.c:215
sys_exit(ffff80002a766d08,ffff8000364bd740,ffff8000364bd690) at sys_exit+0x1a sys/kern/kern_exit.c:-1
syscall(ffff8000364bd740) at syscall+0x962 mi_syscall sys/sys/syscall_mi.h:-1 [inline]
syscall(ffff8000364bd740) at syscall+0x962 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x717bcc6ed070, count: 242
End of stack trace.
syncing disks...