panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/main/kernel/sys/kern/kern_synch.c", line 955
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(ffffffff834154d0) at panic+0x1cf sys/kern/subr_prf.c:198
__assert(ffffffff834536c5,ffffffff834b4195,3bb,ffffffff8348db79) at __assert+0x29 sys/kern/subr_prf.c:-1
refcnt_finalize(ffff80003c92f758,ffffffff83407ecf) at refcnt_finalize+0x1c8 sys/kern/kern_synch.c:956
pppx_if_destroy(285b9a,ffff80003c92f750) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794
pppxclose(285b9a,41,2000,ffff80002a79c2b8) at pppxclose+0xa0 sys/net/if_pppx.c:541
spec_close(ffff8000308d38c0) at spec_close+0x417 sys/kern/spec_vnops.c:-1
VOP_CLOSE(fffffd8068f116f8,41,fffffd8007ffd958,ffff80002a79c2b8) at VOP_CLOSE+0x129 sys/kern/vfs_vops.c:156
vn_closefile(fffffd806d1875b0,ffff80002a79c2b8) at vn_closefile+0x11d vn_close sys/kern/vfs_vnops.c:292 [inline]
vn_closefile(fffffd806d1875b0,ffff80002a79c2b8) at vn_closefile+0x11d sys/kern/vfs_vnops.c:615
fdrop(fffffd806d1875b0,ffff80002a79c2b8) at fdrop+0x121 sys/kern/kern_descrip.c:1281
closef(fffffd806d1875b0,ffff80002a79c2b8) at closef+0x190 sys/kern/kern_descrip.c:1265
fdfree(ffff80002a79c2b8) at fdfree+0x115 sys/kern/kern_descrip.c:1196
exit1(ffff80002a79c2b8,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215
sys_exit(ffff80002a79c2b8,ffff8000308d3c20,ffff8000308d3b70) at sys_exit+0x1a sys/kern/kern_exit.c:-1
end trace frame: 0xffff8000308d3c10, count: 0
https://www.openbsd.org/ddb.html describes the minimum info required in bug
reports.  Insufficient info makes it difficult to find and fix bugs.
ddb> 
ddb> set $lines = 0
ddb> set $maxwidth = 0
ddb> show panic
*cpu0: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/main/kernel/sys/kern/kern_synch.c", line 955
ddb>