syzbot

panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 951
Starting stack trace...
panic(ffffffff83464cd3) at panic+0x1d0 sys/kern/subr_prf.c:229
__assert(ffffffff83413606,ffffffff8341ad18,3b7,ffffffff8341ad9b) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80003c413568,ffffffff83358390) at refcnt_finalize+0x1db sys/kern/kern_synch.c:952
pppx_if_destroy(0,ffff80003c413560) at pppx_if_destroy+0x3d sys/net/if_pppx.c:806
pppxclose(205b9a,41,2000,ffff80002a317770) at pppxclose+0xa0 sys/net/if_pppx.c:553
spec_close(ffff80003c4066c0) at spec_close+0x412 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffd805cdf10d8,41,fffffd80097fb4e0,ffff80002a317770) at VOP_CLOSE+0x133 sys/kern/vfs_vops.c:156
vn_closefile(fffffd8062ca05f0,ffff80002a317770) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd8062ca05f0,ffff80002a317770) at vn_closefile+0x12b sys/kern/vfs_vnops.c:615
fdrop(fffffd8062ca05f0,ffff80002a317770) at fdrop+0x126 sys/kern/kern_descrip.c:1267
closef(fffffd8062ca05f0,ffff80002a317770) at closef+0x192 sys/kern/kern_descrip.c:1251
fdfree(ffff80002a317770) at fdfree+0x116 sys/kern/kern_descrip.c:1182
exit1(ffff80002a317770,0,0,1) at exit1+0x59c sys/kern/kern_exit.c:215
sys_exit(ffff80002a317770,ffff80003c406a30,ffff80003c406980) at sys_exit+0x1a sys/kern/kern_exit.c:-1
syscall(ffff80003c406a30) at syscall+0xb08 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c406a30) at syscall+0xb08 sys/arch/amd64/amd64/trap.c:579
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x77c820621d10, count: 242
End of stack trace.