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 db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438 panic(ffffffff834bd22e) at panic+0x1e5 sys/kern/subr_prf.c:198 __assert(ffffffff834faa34,ffffffff8350c974,3bb,ffffffff83535c39) at __assert+0x29 sys/kern/subr_prf.c:-1 refcnt_finalize(ffff80002a23f148,ffffffff834b047f) at refcnt_finalize+0x1db sys/kern/kern_synch.c:956 pppx_if_destroy(205b9a,ffff80002a23f140) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794 pppxclose(205b9a,81,2000,ffff80002a2342c0) at pppxclose+0xa0 sys/net/if_pppx.c:541 spec_close(ffff80003b7c6b60) at spec_close+0x417 sys/kern/spec_vnops.c:-1 VOP_CLOSE(ffffef006f4af648,81,ffffef00097fd4e0,ffff80002a2342c0) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156 vn_closefile(ffffef0068e62c48,ffff80002a2342c0) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:298 [inline] vn_closefile(ffffef0068e62c48,ffff80002a2342c0) at vn_closefile+0x12b sys/kern/vfs_vnops.c:621 fdrop(ffffef0068e62c48,ffff80002a2342c0) at fdrop+0x121 sys/kern/kern_descrip.c:1281 closef(ffffef0068e62c48,ffff80002a2342c0) at closef+0x192 sys/kern/kern_descrip.c:1265 fdfree(ffff80002a2342c0) at fdfree+0x116 sys/kern/kern_descrip.c:1196 exit1(ffff80002a2342c0,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215 sys_exit(ffff80002a2342c0,ffff80003b7c6ed0,ffff80003b7c6e20) at sys_exit+0x1a sys/kern/kern_exit.c:-1 end trace frame: 0xffff80003b7c6ec0, 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{0}> ddb{0}> set $lines = 0 ddb{0}> set $maxwidth = 0 ddb{0}> show panic *cpu0: kernel diagnostic assertion "refs != ~0" failed: file "/syzkaller/managers/multicore/kernel/sys/kern/kern_synch.c", line 955 ddb{0}> trace db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438 panic(ffffffff834bd22e) at panic+0x1e5 sys/kern/subr_prf.c:198 __assert(ffffffff834faa34,ffffffff8350c974,3bb,ffffffff83535c39) at __assert+0x29 sys/kern/subr_prf.c:-1 refcnt_finalize(ffff80002a23f148,ffffffff834b047f) at refcnt_finalize+0x1db sys/kern/kern_synch.c:956 pppx_if_destroy(205b9a,ffff80002a23f140) at pppx_if_destroy+0x3d sys/net/if_pppx.c:794 pppxclose(205b9a,81,2000,ffff80002a2342c0) at pppxclose+0xa0 sys/net/if_pppx.c:541 spec_close(ffff80003b7c6b60) at spec_close+0x417 sys/kern/spec_vnops.c:-1 VOP_CLOSE(ffffef006f4af648,81,ffffef00097fd4e0,ffff80002a2342c0) at VOP_CLOSE+0x132 sys/kern/vfs_vops.c:156 vn_closefile(ffffef0068e62c48,ffff80002a2342c0) at vn_closefile+0x12b vn_close sys/kern/vfs_vnops.c:298 [inline] vn_closefile(ffffef0068e62c48,ffff80002a2342c0) at vn_closefile+0x12b sys/kern/vfs_vnops.c:621 fdrop(ffffef0068e62c48,ffff80002a2342c0) at fdrop+0x121 sys/kern/kern_descrip.c:1281 closef(ffffef0068e62c48,ffff80002a2342c0) at closef+0x192 sys/kern/kern_descrip.c:1265 fdfree(ffff80002a2342c0) at fdfree+0x116 sys/kern/kern_descrip.c:1196 exit1(ffff80002a2342c0,0,0,1) at exit1+0x576 sys/kern/kern_exit.c:215 sys_exit(ffff80002a2342c0,ffff80003b7c6ed0,ffff80003b7c6e20) at sys_exit+0x1a sys/kern/kern_exit.c:-1 syscall(ffff80003b7c6ed0) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline] syscall(ffff80003b7c6ed0) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x754f62b70e50, count: -16 ddb{0}> show registers rdi 0 rsi 0x1 rbp 0xffff80003b7c6930 rbx 0xffffffff83977e07 cpu_info_full_primary+0x2e07 rdx 0 rcx 0xffff80002a2342c0 rax 0xffffffff83976ff0 cpu_info_full_primary+0x1ff0 r8 0x101010101010101 r9 0x8080808080808080 r10 0x34067bd6b45f03f3 r11 0xda6d246ac76ef42d r12 0xffffffff83977c08 cpu_info_full_primary+0x2c08 r13 0 r14 0 r15 0x1 rip 0xffffffff8266fa25 db_enter+0x25 cs 0x8 rflags 0x246 rsp 0xffff80003b7c6920 ss 0x10 db_enter+0x25: addq $0x8,%rsp ddb{0}> show proc PROC (syz-executor) tid=298095 pid=52167 tcnt=0 stat=onproc flags process=1008 proc=2000 runpri=32, usrpri=86, slppri=32, nice=20 wchan=0x0, wmesg=, ps_single=0xffff80002a2342c0 scnt=-1 ecnt=1 forw=0xffffffffffffffff, list=0xffff80002a234028,0xffff8000333a0fc0 process=0xffff8000373a4020 user=0xffff80003b7c1000, vmspace=0xffffef006b71b7c0 estcpu=36, cpticks=6, pctcpu=0.0, user=0, sys=1, intr=0 ddb{0}> ps PID TID PPID UID S FLAGS WAIT COMMAND 3074 190190 84060 0 2 0 syz-executor 23669 240167 69721 0 3 0x3000 suspend syz-executor 23669 25914 69721 0 3 0x4081000 smrbar syz-executor 55349 280673 7176 -1 3 0x90 nanoslp syz-executor 55349 518759 7176 -1 3 0x4000090 wsevent_read syz-executor 55349 167870 7176 -1 3 0x4000090 fsleep syz-executor 39079 29722 37945 0 2 0 syz-executor 39079 190251 37945 0 3 0x4000080 ttyretype syz-executor 39079 288518 37945 0 3 0x4000080 fsleep syz-executor 39079 94050 37945 0 3 0x4000080 fsleep syz-executor 7439 508951 28813 0 2 0 syz-executor 7439 225361 28813 0 2 0x4000000 syz-executor 7439 425005 28813 0 3 0x4000000 inode syz-executor 7439 58174 28813 0 3 0x4000000 inode syz-executor 7439 166030 28813 0 3 0x4000080 fsleep syz-executor 55797 246652 0 0 3 0x14280 nfsidl nfsio 87102 168752 0 0 3 0x14280 nfsidl nfsio 16849 248767 0 0 3 0x14280 nfsidl nfsio 55318 407824 0 0 3 0x14280 nfsidl nfsio 70293 436381 0 0 3 0x14280 nfsidl nfsio 24229 516489 0 0 3 0x14280 nfsidl nfsio 41156 97184 0 0 3 0x14280 nfsidl nfsio 80295 328278 0 0 3 0x14280 nfsidl nfsio 83531 468178 0 0 3 0x14280 nfsidl nfsio 22694 440110 0 0 3 0x14280 nfsidl nfsio 95941 138236 0 0 3 0x14280 nfsidl nfsio 81732 517477 0 0 3 0x14280 nfsidl nfsio 54736 239318 0 0 3 0x14280 nfsidl nfsio 92510 182585 0 0 3 0x14280 nfsidl nfsio 12348 18165 0 0 3 0x14280 nfsidl nfsio 85724 354742 0 0 3 0x14280 nfsidl nfsio 73556 201726 0 0 3 0x14280 nfsidl nfsio 77159 146045 0 0 3 0x14280 nfsidl nfsio 22803 272629 0 0 3 0x14280 nfsidl nfsio 65748 212746 0 0 3 0x14280 nfsidl nfsio 85678 355256 0 0 3 0x14200 acct acct 2072 478464 1 0 3 0x100083 ttyin getty 69721 178831 32016 0 3 0x82 nanoslp syz-executor 28813 114178 32016 0 2 0xc82 syz-executor 37945 493800 32016 0 3 0x82 nanoslp syz-executor 7176 214253 32016 0 2 0xc82 syz-executor 62177 201106 32016 0 3 0x82 nanoslp syz-executor 84060 266196 32016 0 2 0x2 syz-executor 2818 382242 32016 0 3 0x82 wait syz-executor 78836 39450 32016 0 2 0xc82 syz-executor 32016 89294 1 0 3 0x82 kqread syz-executor 27498 242961 0 0 3 0x14200 bored smr 40990 218415 0 0 2 0x14200 zerothread 21823 280465 0 0 3 0x14200 aiodoned aiodoned 40662 139382 0 0 3 0x14200 syncer update 12763 462006 0 0 3 0x14200 cleaner cleaner 77788 13889 0 0 3 0x14200 reaper reaper 86379 380439 0 0 3 0x14200 pgdaemon pagedaemon 86475 514638 0 0 3 0x14200 bored viomb 29146 231893 0 0 3 0x40014200 acpi0 acpi0 2027 78103 0 0 7 0x40014200 idle1 63458 232593 0 0 3 0x14200 bored softnet1 82512 216043 0 0 2 0x14200 softnet0 23558 220326 0 0 3 0x14200 smrbar systqmp 31088 80347 0 0 3 0x14200 bored systq 74446 237588 0 0 3 0x14200 tmoslp softclockmp 26252 282532 0 0 3 0x40014200 tmoslp softclock 65764 217131 0 0 3 0x40014200 idle0 1 246509 0 0 3 0x82 wait init 0 0 -1 0 3 0x10200 scheduler swapper ddb{0}> show all locks Process 7439 (syz-executor) thread 0xffff8000333a1ca8 (225361) exclusive rrwlock inode r = 0 (0xffffef006b6fd8e0) #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 vn_write+0x18f sys/kern/vfs_vnops.c:411 #6 dofilewritev+0x2bd sys/kern/sys_generic.c:384 #7 sys_write+0xa2 sys/kern/sys_generic.c:300 #8 syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline] #8 syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783 #9 Xsyscall+0x128 Process 7439 (syz-executor) thread 0xffff80002a223c98 (58174) exclusive rrwlock inode r = 0 (0xffffef006e4f6368) #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 vn_open+0x22e sys/kern/vfs_vnops.c:109 #8 doopenat+0x35b sys/kern/vfs_syscalls.c:1162 #9 sys_open+0x59 sys/kern/vfs_syscalls.c:1064 #10 syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline] #10 syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783 #11 Xsyscall+0x128 Process 23558 (systqmp) thread 0xffff8000ffffe530 (220326) shared rwlock systqmp r = 0 (0xffffffff839d03c8) #0 witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline] #0 witness_lock+0x5f1 sys/kern/subr_witness.c:1160 #1 taskq_thread+0x12a sys/kern/kern_task.c:442 #2 proc_trampoline+0x10 ddb{0}> show malloc Type InUse MemUse HighUse Limit Requests Type Lim devbuf 11116 12493K 12745K 166960K 12893 0 pcb 18 14K 15K 166960K 96 0 rtable 255 10K 10K 166960K 432 0 pf 51 20K 22K 166960K 109 0 ifaddr 52 8K 8K 166960K 74 0 ifgroup 78 3K 3K 166960K 123 0 sysctl 1 1K 9K 166960K 5 0 counters 88 39K 39K 166960K 130 0 ioctlops 0 0K 4K 166960K 1588 0 iov 0 0K 16K 166960K 21 0 mount 1 1K 1K 166960K 1 0 log 36 8K 8K 166960K 40 0 vnodes 1360 85K 85K 166960K 2067 0 UFS quota 1 32K 32K 166960K 1 0 UFS mount 5 36K 36K 166960K 5 0 shm 2 1K 5K 166960K 10 0 VM map 2 1K 1K 166960K 2 0 sem 12 0K 0K 166960K 29 0 dirhash 12 2K 3K 166960K 18 0 ACPI 1692 195K 286K 166960K 12470 0 file desc 17 65K 93K 166960K 524 0 sigio 0 0K 0K 166960K 5 0 proc 21 33K 180K 166960K 622 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 41 0 in_multi 96 7K 7K 166960K 115 0 ether_multi 1 0K 0K 166960K 2 0 mrt 1 0K 0K 166960K 21 0 ISOFS mount 1 32K 32K 166960K 1 0 MSDOSFS mount 1 16K 16K 166960K 1 0 ttys 151 678K 678K 166960K 151 0 exec 0 0K 1K 166960K 418 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 158 83K 176K 166960K 6612 0 UVM aobj 22 2K 2K 166960K 22 0 pinsyscall 20 40K 104K 166960K 1687 0 memdesc 1 4K 4K 166960K 1 0 crypto data 1 1K 1K 166960K 1 0 ip6_options 0 0K 0K 166960K 24 0 NDP 19 0K 1K 166960K 51 0 temp 49 9117K 9174K 166960K 38931 0 kqueue 2 2K 22K 166960K 96 0 SYN cache 2 16K 16K 166960K 2 0 ddb{0}>