syzbot

panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 953
Starting stack trace...
panic(ffffffff8336f3d2) at panic+0x1d0 sys/kern/subr_prf.c:229
__assert(ffffffff833b011a,ffffffff833c28e5,3b9,ffffffff833ec850) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80002a33b4f0,ffffffff8336bfb1) at refcnt_finalize+0x1db sys/kern/kern_synch.c:954
pppx_if_destroy(205b9a,ffff80002a33b4e8) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794
pppxclose(205b9a,2,2000,ffff800033811790) at pppxclose+0xa0 sys/net/if_pppx.c:541
spec_close(ffff80003c4934d0) at spec_close+0x417 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffd80666ea798,2,fffffd80097fb5b0,ffff800033811790) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156
vn_closefile(fffffd805d05eb88,ffff800033811790) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd805d05eb88,ffff800033811790) at vn_closefile+0x12b sys/kern/vfs_vnops.c:615
fdrop(fffffd805d05eb88,ffff800033811790) at fdrop+0x121 sys/kern/kern_descrip.c:1280
closef(fffffd805d05eb88,ffff800033811790) at closef+0x192 sys/kern/kern_descrip.c:1264
fdfree(ffff800033811790) at fdfree+0x116 sys/kern/kern_descrip.c:1195
exit1(ffff800033811790,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215
sys_exit(ffff800033811790,ffff80003c493840,ffff80003c493790) at sys_exit+0x1a sys/kern/kern_exit.c:-1
syscall(ffff80003c493840) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c493840) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:746
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7da2ac098140, count: 242
End of stack trace.