panic: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 955 Stopped at db_enter+0x25: addq $0x8,%rsp TID PID UID PRFLAGS PFLAGS CPU COMMAND 488644 42032 0 0 0 0 syz-executor db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438 panic(ffffffff834b854b) at panic+0x1e5 sys/kern/subr_prf.c:198 __assert(ffffffff834f8d99,ffffffff83503ca3,3bb,ffffffff8352c728) at __assert+0x29 sys/kern/subr_prf.c:-1 refcnt_finalize(ffff80003c3c7770,ffffffff834b2810) at refcnt_finalize+0x1db sys/kern/kern_synch.c:956 pppx_if_destroy(285b9a,ffff80003c3c7768) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794 pppxclose(285b9a,41,2000,ffff80003c400028) at pppxclose+0xa0 sys/net/if_pppx.c:541 spec_close(ffff80003c3ac730) at spec_close+0x417 sys/kern/spec_vnops.c:-1 VOP_CLOSE(fffffb006a075a30,41,fffffb00097fd618,ffff80003c400028) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156 vn_closefile(fffffb006e90a330,ffff80003c400028) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:298 [inline] vn_closefile(fffffb006e90a330,ffff80003c400028) at vn_closefile+0x12b sys/kern/vfs_vnops.c:621 fdrop(fffffb006e90a330,ffff80003c400028) at fdrop+0x121 sys/kern/kern_descrip.c:1281 closef(fffffb006e90a330,ffff80003c400028) at closef+0x192 sys/kern/kern_descrip.c:1265 fdfree(ffff80003c400028) at fdfree+0x116 sys/kern/kern_descrip.c:1196 exit1(ffff80003c400028,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215 sys_exit(ffff80003c400028,ffff80003c3acaa0,ffff80003c3ac9f0) at sys_exit+0x1a sys/kern/kern_exit.c:-1 end trace frame: 0xffff80003c3aca90, 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{1}> ddb{1}> set $lines = 0 ddb{1}> set $maxwidth = 0 ddb{1}> show panic *cpu1: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 955 ddb{1}> trace db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438 panic(ffffffff834b854b) at panic+0x1e5 sys/kern/subr_prf.c:198 __assert(ffffffff834f8d99,ffffffff83503ca3,3bb,ffffffff8352c728) at __assert+0x29 sys/kern/subr_prf.c:-1 refcnt_finalize(ffff80003c3c7770,ffffffff834b2810) at refcnt_finalize+0x1db sys/kern/kern_synch.c:956 pppx_if_destroy(285b9a,ffff80003c3c7768) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794 pppxclose(285b9a,41,2000,ffff80003c400028) at pppxclose+0xa0 sys/net/if_pppx.c:541 spec_close(ffff80003c3ac730) at spec_close+0x417 sys/kern/spec_vnops.c:-1 VOP_CLOSE(fffffb006a075a30,41,fffffb00097fd618,ffff80003c400028) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156 vn_closefile(fffffb006e90a330,ffff80003c400028) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:298 [inline] vn_closefile(fffffb006e90a330,ffff80003c400028) at vn_closefile+0x12b sys/kern/vfs_vnops.c:621 fdrop(fffffb006e90a330,ffff80003c400028) at fdrop+0x121 sys/kern/kern_descrip.c:1281 closef(fffffb006e90a330,ffff80003c400028) at closef+0x192 sys/kern/kern_descrip.c:1265 fdfree(ffff80003c400028) at fdfree+0x116 sys/kern/kern_descrip.c:1196 exit1(ffff80003c400028,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215 sys_exit(ffff80003c400028,ffff80003c3acaa0,ffff80003c3ac9f0) at sys_exit+0x1a sys/kern/kern_exit.c:-1 syscall(ffff80003c3acaa0) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline] syscall(ffff80003c3acaa0) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x7435c6d147f0, count: -16 ddb{1}> show registers rdi 0 rsi 0x1 rbp 0xffff80003c3ac500 rbx 0xffff80002999ee07 rdx 0 rcx 0xffff80003c400028 rax 0xffff80002999dff0 r8 0x101010101010101 r9 0x8080808080808080 r10 0xff3e8a40e76e24f0 r11 0x83d3ff96393475a6 r12 0xffff80002999ec08 r13 0 r14 0 r15 0x1 rip 0xffffffff8224d3a5 db_enter+0x25 cs 0x8 rflags 0x246 rsp 0xffff80003c3ac4f0 ss 0x10 db_enter+0x25: addq $0x8,%rsp ddb{1}> show proc PROC (syz-executor) tid=214409 pid=15839 tcnt=0 stat=onproc flags process=1008 proc=2000 runpri=32, usrpri=86, slppri=32, nice=20 wchan=0x0, wmesg=, ps_single=0xffff80003c400028 scnt=-1 ecnt=1 forw=0xffffffffffffffff, list=0xffff80003c401a18,0xffff80003c4014f8 process=0xffff8000ffff1820 user=0xffff80003c3a7000, vmspace=0xfffffb000b0633d0 estcpu=36, cpticks=3, pctcpu=0.0, user=0, sys=2, intr=0 ddb{1}> ps PID TID PPID UID S FLAGS WAIT COMMAND 42032 488644 4339 0 7 0 syz-executor 42032 204444 4339 0 2 0x4000000 syz-executor 37695 188706 77570 0 2 0 syz-executor 37695 488519 77570 0 3 0x4000080 fsleep syz-executor 37695 134497 77570 0 2 0x4000000 syz-executor 81198 297458 51940 0 2 0 syz-executor 81198 457486 51940 0 2 0x4000000 syz-executor 81198 24645 51940 0 3 0x4000080 fsleep syz-executor 24849 301631 5466 0 2 0 syz-executor 24849 126945 5466 0 3 0x4000080 kqsel syz-executor 24849 442634 5466 0 3 0x4000000 smrbar syz-executor 40693 7478 44464 0 3 0x80 nanoslp syz-executor 40693 279394 44464 0 3 0x4000080 fifor syz-executor 40693 83643 44464 0 3 0x4000080 fsleep syz-executor 23075 418557 1 0 3 0x80 nanoslp init 1937 386523 0 0 3 0x14200 acct acct 5466 249085 50055 0 3 0x82 nanoslp syz-executor 4339 166903 50055 0 3 0x82 nanoslp syz-executor 66530 89331 50055 0 3 0x2 biowait syz-executor 51940 193002 50055 0 3 0x82 nanoslp syz-executor 77570 12803 50055 0 3 0x82 nanoslp syz-executor 91456 64524 50055 0 3 0x82 piperd syz-executor 44464 446487 50055 0 3 0x82 nanoslp syz-executor 85612 32820 50055 0 3 0x82 nanoslp syz-executor 50055 372993 1 0 2 0x2 syz-executor 94641 311235 0 0 3 0x14200 bored smr 54161 456564 0 0 2 0x14200 zerothread 57760 422357 0 0 3 0x14200 aiodoned aiodoned 38094 446197 0 0 3 0x14200 syncer update 50433 271596 0 0 3 0x14200 cleaner cleaner 99019 34708 0 0 3 0x14200 reaper reaper 30689 460555 0 0 3 0x14200 pgdaemon pagedaemon 53332 443926 0 0 3 0x14200 bored viomb 52141 19107 0 0 3 0x40014200 acpi0 acpi0 82771 337580 0 0 3 0x40014200 idle1 54969 257659 0 0 3 0x14200 bored softnet1 34701 106820 0 0 3 0x14200 bored softnet0 12497 420200 0 0 3 0x14200 bored systqmp 28833 452788 0 0 3 0x14200 bored systq 85609 75069 0 0 3 0x14200 tmoslp softclockmp 334 352275 0 0 3 0x40014200 tmoslp softclock 32521 513740 0 0 3 0x40014200 idle0 1 405632 0 0 3 0x82 wait init 0 0 -1 0 3 0x10200 scheduler swapper ddb{1}> show all locks Process 66530 (syz-executor) thread 0xffff80002a221a08 (89331) exclusive rrwlock inode r = 0 (0xfffffb006e496c78) #0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline] #0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160 #1 rw_do_enter_write+0x419 sys/kern/kern_rwlock.c:320 #2 rrw_enter+0xc6 sys/kern/kern_rwlock.c:621 #3 VOP_LOCK+0xbd sys/kern/vfs_vops.c:527 #4 vn_lock+0xa4 sys/kern/vfs_vnops.c:576 #5 vget+0x2a2 sys/kern/vfs_subr.c:686 #6 ufs_ihashget+0x185 sys/ufs/ufs/ufs_ihash.c:98 #7 ffs_vget+0x8c sys/ufs/ffs/ffs_vfsops.c:1203 #8 ufs_lookup+0x1a36 sys/ufs/ufs/ufs_lookup.c:478 #9 VOP_LOOKUP+0x6e sys/kern/vfs_vops.c:85 #10 vfs_lookup+0x963 sys/kern/vfs_lookup.c:580 #11 namei+0x7c5 sys/kern/vfs_lookup.c:250 #12 dounlinkat+0xc1 sys/kern/vfs_syscalls.c:1806 #13 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline] #13 syscall+0xb17 sys/arch/amd64/amd64/trap.c:783 #14 Xsyscall+0x128 exclusive rrwlock inode r = 0 (0xfffffb006ca4e1e0) #0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline] #0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160 #1 rw_do_enter_write+0x419 sys/kern/kern_rwlock.c:320 #2 rrw_enter+0xc6 sys/kern/kern_rwlock.c:621 #3 VOP_LOCK+0xbd sys/kern/vfs_vops.c:527 #4 vn_lock+0xa4 sys/kern/vfs_vnops.c:576 #5 vfs_lookup+0x12b sys/kern/vfs_lookup.c:431 #6 namei+0x7c5 sys/kern/vfs_lookup.c:250 #7 dounlinkat+0xc1 sys/kern/vfs_syscalls.c:1806 #8 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline] #8 syscall+0xb17 sys/arch/amd64/amd64/trap.c:783 #9 Xsyscall+0x128 ddb{1}> show malloc Type InUse MemUse HighUse Limit Requests Type Lim devbuf 11083 12293K 12348K 166960K 12395 0 pcb 17 14K 15K 166960K 67 0 rtable 243 9K 9K 166960K 416 0 pf 39 18K 24K 166960K 87 0 ifaddr 41 7K 7K 166960K 49 0 ifgroup 56 2K 2K 166960K 64 0 sysctl 1 1K 9K 166960K 6 0 counters 72 37K 37K 166960K 78 0 ioctlops 0 0K 4K 166960K 1523 0 iov 0 0K 16K 166960K 11 0 mount 1 1K 1K 166960K 1 0 log 1 0K 0K 166960K 5 0 vnodes 1289 81K 82K 166960K 1534 0 UFS quota 1 32K 32K 166960K 1 0 UFS mount 5 36K 36K 166960K 5 0 shm 2 1K 5K 166960K 7 0 VM map 2 1K 1K 166960K 2 0 sem 10 0K 0K 166960K 17 0 dirhash 12 2K 2K 166960K 12 0 ACPI 1692 195K 286K 166960K 12470 0 file desc 15 57K 240K 166960K 366 0 sigio 0 0K 0K 166960K 1 0 proc 12 17K 147K 166960K 578 0 subproc 72 4K 4K 166960K 72 0 NFS srvsock 1 0K 0K 166960K 1 0 NFS daemon 1 16K 16K 166960K 1 0 ip_moptions 0 0K 0K 166960K 29 0 in_multi 89 6K 7K 166960K 105 0 ether_multi 1 0K 0K 166960K 3 0 mrt 0 0K 0K 166960K 11 0 ISOFS mount 1 32K 32K 166960K 1 0 MSDOSFS mount 1 16K 16K 166960K 1 0 ttys 127 572K 572K 166960K 127 0 exec 0 0K 1K 166960K 404 0 fusefs mount 1 32K 32K 166960K 1 0 tdb 3 0K 0K 166960K 3 0 VM swap 8 62K 64K 166960K 10 0 UVM amap 123 78K 165K 166960K 5087 0 UVM aobj 10 2K 2K 166960K 10 0 pinsyscall 17 34K 103K 166960K 1514 0 memdesc 1 4K 4K 166960K 1 0 crypto data 1 1K 1K 166960K 1 0 ip6_options 0 0K 0K 166960K 8 0 NDP 12 0K 2K 166960K 31 0 temp 41 9111K 9174K 166960K 19972 0 kqueue 2 4K 26K 166960K 67 0 SYN cache 2 16K 16K 166960K 2 0 ddb{1}> show all pools Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle plcache 128 26 0 0 1 0 1 1 0 8 0 rtpcb 120 46 0 46 1 0 1 1 0 8 1 rtentry 176 117 0 14 6 0 6 6 0 8 0 unpcb 144 132 0 128 1 0 1 1 0 8 0 syncache 336 5 0 5 1 0 1 1 0 8 1 tcpcb 736 192 0 189 7 1 6 7 0 8 5 arp 136 19 0 2 1 0 1 1 0 8 0 inpcb 328 556 0 552 7 0 7 7 0 8 6 nd6 152 26 0 3 1 0 1 1 0 8 0 pkpcb 40 2 0 2 1 0 1 1 0 8 1 kcovpl 48 8 0 0 1 0 1 1 0 8 0 ppxss 1192 3 0 2 1 0 1 1 0 8 0 pppxif 1576 1 0 0 1 0 1 1 0 8 0 pfstscr 40 2 0 2 1 0 1 1 0 8 1 pffrag 232 3 0 1 1 0 1 1 0 482 0 pffrnode 88 3 0 1 1 0 1 1 0 8 0 pffrent 40 8 0 6 1 0 1 1 0 8 0 pfosfp 40 1428 0 1428 5 0 5 5 0 8 5 pfosfpen 112 1428 0 1428 21 0 21 21 0 8 21 pfsrclim 320 1 0 1 1 0 1 1 0 8 1 pfanchor 1288 11 0 9 1 0 1 1 0 8 0 pftag 88 1 0 1 1 0 1 1 0 8 1 pfstitem 24 35 0 1 1 0 1 1 0 8 0 pfstkey 128 37 0 3 2 0 2 2 0 8 0 pfstate 448 35 0 2 4 0 4 4 0 8 0 pfrule 1360 26 0 19 2 1 1 2 0 8 0 art_heap8 4096 2 0 0 2 0 2 2 0 8 0 art_heap4 256 463 0 44 29 0 29 29 0 8 2 art_table 40 465 0 44 5 0 5 5 0 8 0 art_node 32 115 0 21 1 0 1 1 0 8 0 sysvmsgpl 40 3 0 0 1 0 1 1 0 8 0 semupl 112 2 0 2 1 0 1 1 0 8 1 semapl 72 15 0 7 1 0 1 1 0 8 0 shmpl 112 7 0 0 1 0 1 1 0 8 0 dirhash 1024 17 0 0 3 0 3 3 0 8 0 dino2pl 256 1966 0 493 93 0 93 93 0 8 0 ffsino 296 1966 0 493 115 0 115 115 0 8 1 nchpl 144 2462 0 757 64 0 64 64 0 8 0 vnodes 216 2160 0 0 120 0 120 120 0 8 0 namei 1024 7895 0 7895 2 0 2 2 0 8 2 percpumem 16 54 0 3 1 0 1 1 0 8 0 kstatmem 264 33 0 6 2 0 2 2 0 8 0 scsiplug 72 1 0 1 1 0 1 1 0 8 1 scxspl 216 9971 0 9970 5 3 2 3 1 8 1 plimitpl 152 123 0 114 1 0 1 1 0 8 0 sigapl 424 673 0 638 7 1 6 7 0 8 0 knotepl 120 461 0 0 14 0 14 14 0 8 0 kqueuepl 224 84 0 77 1 0 1 1 0 8 0 pipepl 344 140 0 112 3 0 3 3 0 8 0 fdescpl 528 656 0 638 3 0 3 3 0 8 0 filepl 160 3369 0 3198 12 1 11 12 0 8 2 lockfpl 104 269 0 268 1 0 1 1 0 8 0 lockfspl 48 71 0 70 1 0 1 1 0 8 0 sessionpl 144 38 0 36 1 0 1 1 0 8 0 pgrppl 48 49 0 39 1 0 1 1 0 8 0 ucredpl 104 455 0 452 1 0 1 1 0 8 0 zombiepl 144 639 0 638 1 0 1 1 0 8 0 processpl 1232 673 0 638 5 1 4 5 0 8 0 procpl 664 1055 0 1011 6 0 6 6 0 8 1 sockpl 752 747 0 739 10 2 8 10 0 8 6 mcl64k 65536 3 0 0 1 0 1 1 0 8 0 mcl8k 8192 3 0 0 1 0 1 1 0 8 0 mcl4k 4096 123 0 0 16 0 16 16 0 8 0 mcl2k2 2112 1 0 0 1 0 1 1 0 8 0 mcl2k 2048 20 0 0 3 0 3 3 0 8 0 mtagpl 96 4 0 0 1 0 1 1 0 8 0 mbufpl 256 156 0 0 10 0 10 10 0 8 0 bufpl 280 4550 0 106 318 0 318 318 0 8 0 anonpl 32 3804 0 0 31 0 31 31 0 246 0 amapchunkpl 152 15846 0 15510 29 1 28 28 0 158 11 amappl16 200 2030 0 2006 6 3 3 5 0 8 0 amappl15 192 7 0 7 1 1 0 1 0 8 0 amappl14 184 431 0 431 1 1 0 1 0 8 0 amappl13 176 125 0 125 1 0 1 1 0 8 1 amappl12 168 905 0 889 2 0 2 2 0 8 0 amappl11 160 5 0 4 1 0 1 1 0 8 0 amappl10 152 63 0 63 1 0 1 1 0 8 1 amappl9 144 368 0 368 1 1 0 1 0 8 0 amappl8 136 102 0 102 1 0 1 1 0 8 1 amappl7 128 150 0 148 1 0 1 1 0 8 0 amappl6 120 155 0 155 1 1 0 1 0 8 0 amappl5 112 100 0 98 1 0 1 1 0 8 0 amappl4 104 290 0 289 1 0 1 1 0 8 0 amappl3 96 2952 0 2879 3 0 3 3 0 8 0 amappl2 88 561 0 553 2 0 2 2 0 8 0 amappl1 80 11371 0 11281 14 2 12 14 0 8 7 amappl 88 4271 0 4158 4 0 4 4 0 92 0 uvmvnodes 80 111 0 0 3 0 3 3 0 8 0 dma4096 4096 1 0 1 1 1 0 1 0 8 0 dma1024 1024 1 0 0 1 0 1 1 0 8 0 dma256 256 6 0 6 1 1 0 1 0 8 0 dma128 128 253 0 253 1 1 0 1 0 8 0 dma64 64 6 0 6 1 1 0 1 0 8 0 dma32 32 7 0 7 1 1 0 1 0 8 0 dma16 16 18 0 17 1 0 1 1 0 8 0 aobjpl 72 9 0 0 1 0 1 1 0 8 0 uaddrrnd 24 656 0 638 1 0 1 1 0 8 0 uaddrbest 32 2 0 0 1 0 1 1 0 8 0 uaddr 24 656 0 638 1 0 1 1 0 8 0 vmmpekpl 168 7209 0 7172 2 0 2 2 0 8 0 vmmpepl 168 50584 0 49821 86 1 85 86 0 357 43 vmsppl 488 655 0 638 5 1 4 5 0 8 0 rwobjpl 80 17060 0 16665 23 1 22 23 0 8 0 pdppl 4096 1319 0 1276 99 52 47 87 0 8 4 pvpl 32 9863 0 0 80 0 80 80 0 265 0 pmappl 256 655 0 638 3 0 3 3 0 8 0 extentpl 40 45 0 27 1 0 1 1 0 8 0 phpool 112 279 0 56 8 0 8 8 0 8 0 ddb{1}> machine ddbcpu 0 Stopped at x86_ipi_db+0x27: addq $0x8,%rsp x86_ipi_db(ffffffff838f1ff0) at x86_ipi_db+0x27 sys/arch/amd64/amd64/db_interface.c:394 x86_ipi_handler() at x86_ipi_handler+0xd9 sys/arch/amd64/amd64/ipi.c:106 Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27 __sanitizer_cov_trace_pc() at __sanitizer_cov_trace_pc+0x33 kd_curproc sys/dev/kcov.c:585 [inline] __sanitizer_cov_trace_pc() at __sanitizer_cov_trace_pc+0x33 sys/dev/kcov.c:153 __mp_lock(ffffffff83b14d40) at _