panic: Data modified on freelist: word 4 of object 0xffff800000a24000 size 0x14 previous type free (0x0 != 0xdeadbeef) Stopped at db_enter+0x18: addq $0x8,%rsp TID PID UID PRFLAGS PFLAGS CPU COMMAND *382647 23153 0 0x2 0x4000001 0 syz-fuzzer db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398 panic(ffffffff821c7b2f) at panic+0x15c sys/kern/subr_prf.c:207 malloc(14,7f,1) at malloc+0xa23 sys/kern/kern_malloc.c:331 ktrgenio(ffff80001d3a7eb0,b,0,ffff800000064f20,c) at ktrgenio+0x163 sys/kern/kern_ktrace.c:243 dofilereadv(ffff80001d3a7eb0,b,ffff800020449378,0,ffff800020449460) at dofilereadv+0x2de sys/kern/sys_generic.c:253 sys_read(ffff80001d3a7eb0,ffff800020449410,ffff800020449460) at sys_read+0x83 sys/kern/sys_generic.c:157 syscall(ffff8000204494e0) at syscall+0x507 sys/arch/amd64/amd64/trap.c:570 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0xc0030c7878, count: 7 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 Data modified on freelist: word 4 of object 0xffff800000a24000 size 0x14 previous type free (0x0 != 0xdeadbeef) ddb> trace db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398 panic(ffffffff821c7b2f) at panic+0x15c sys/kern/subr_prf.c:207 malloc(14,7f,1) at malloc+0xa23 sys/kern/kern_malloc.c:331 ktrgenio(ffff80001d3a7eb0,b,0,ffff800000064f20,c) at ktrgenio+0x163 sys/kern/kern_ktrace.c:243 dofilereadv(ffff80001d3a7eb0,b,ffff800020449378,0,ffff800020449460) at dofilereadv+0x2de sys/kern/sys_generic.c:253 sys_read(ffff80001d3a7eb0,ffff800020449410,ffff800020449460) at sys_read+0x83 sys/kern/sys_generic.c:157 syscall(ffff8000204494e0) at syscall+0x507 sys/arch/amd64/amd64/trap.c:570 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0xc0030c7878, count: -8 ddb> show registers rdi 0 rsi 0x1 rbp 0xffff800020449030 rbx 0xffff8000204490e0 rdx 0x2 rcx 0 rax 0 r8 0xffff800020448ff0 r9 0x1 r10 0 r11 0xbd7ca5e1b36d5b9 r12 0x3000000008 r13 0xffff800020449040 r14 0x100 r15 0x1 rip 0xffffffff82195b58 db_enter+0x18 cs 0x8 rflags 0x246 rsp 0xffff800020449020 ss 0x10 db_enter+0x18: addq $0x8,%rsp ddb> show proc PROC (syz-fuzzer) pid=382647 stat=onproc flags process=2 proc=4000001 pri=50, usrpri=50, nice=20 forw=0xffffffffffffffff, list=0xffff80001d33a118,0xffff80001d35e138 process=0xffff80001d38e380 user=0xffff800020444000, vmspace=0xfffffd806bc0a110 estcpu=0, cpticks=2, pctcpu=0.0 user=0, sys=2, intr=0 ddb> ps PID TID PPID UID S FLAGS WAIT COMMAND 90466 483529 0 0 3 0x14200 acct acct 84635 133343 0 0 3 0x14200 bored sosplice 18122 224459 23153 0 2 0x2 syz-executor.0 90543 24315 23153 0 3 0x2 biowait syz-executor.1 23153 295118 91167 0 3 0x82 thrsleep syz-fuzzer 23153 508047 91167 0 3 0x4000082 nanosleep syz-fuzzer 23153 257884 91167 0 3 0x4000082 thrsleep syz-fuzzer 23153 242570 91167 0 3 0x4000082 thrsleep syz-fuzzer 23153 165108 91167 0 3 0x4000082 thrsleep syz-fuzzer 23153 133946 91167 0 3 0x4000082 thrsleep syz-fuzzer 23153 287683 91167 0 3 0x4000082 thrsleep syz-fuzzer *23153 382647 91167 0 7 0x4000003 syz-fuzzer 91167 78801 73327 0 3 0x10008a pause ksh 73327 98748 53834 0 2 0x12 sshd 12922 305781 1 0 3 0x100083 ttyin getty 53834 482556 1 0 3 0x80 select sshd 29800 21957 92714 73 3 0x100090 kqread syslogd 92714 437080 1 0 3 0x100082 netio syslogd 78599 323239 1 77 3 0x100090 poll dhclient 49835 248492 1 0 3 0x80 poll dhclient 28541 266598 0 0 3 0x14200 bored smr 72468 520822 0 0 3 0x14200 pgzero zerothread 58683 140818 0 0 3 0x14200 aiodoned aiodoned 67397 448591 0 0 3 0x14200 syncer update 11818 45405 0 0 3 0x14200 cleaner cleaner 31024 397262 0 0 3 0x14200 reaper reaper 38062 55027 0 0 3 0x14200 pgdaemon pagedaemon 61382 158936 0 0 3 0x14200 bored crynlk 39421 276820 0 0 3 0x14200 bored crypto 25755 288254 0 0 3 0x40014200 acpi0 acpi0 42173 303168 0 0 3 0x14200 bored softnet 7986 391163 0 0 3 0x14200 bored systqmp 7261 206376 0 0 3 0x14200 bored systq 15279 55979 0 0 3 0x40014200 bored softclock 91944 234982 0 0 3 0x40014200 idle0 1 219768 0 0 3 0x82 wait init 0 0 -1 0 3 0x10200 scheduler swapper ddb> show all locks No such command ddb> show malloc Type InUse MemUse HighUse Limit Requests Type Lim devbuf 9512 6473K 6727K 78643K 10963 0 pcb 13 8K 8K 78643K 66 0 rtable 108 3K 4K 78643K 264 0 ifaddr 73 14K 14K 78643K 113 0 counters 21 16K 16K 78643K 25 0 ioctlops 0 0K 2K 78643K 25 0 iov 0 0K 12K 78643K 39 0 mount 1 1K 1K 78643K 1 0 vnodes 1220 77K 77K 78643K 1343 0 UFS quota 1 32K 32K 78643K 1 0 UFS mount 5 36K 36K 78643K 5 0 shm 2 1K 5K 78643K 5 0 VM map 2 0K 0K 78643K 2 0 sem 12 0K 0K 78643K 32 0 dirhash 12 2K 2K 78643K 12 0 ACPI 1794 195K 288K 78643K 12646 0 file desc 4 9K 25K 78643K 208 0 sigio 0 0K 0K 78643K 4 0 proc 49 38K 54K 78643K 365 0 subproc 32 2K 2K 78643K 34 0 NFS srvsock 1 0K 0K 78643K 1 0 NFS daemon 1 16K 16K 78643K 1 0 ip_moptions 0 0K 0K 78643K 27 0 in_multi 49 2K 3K 78643K 85 0 ether_multi 1 0K 0K 78643K 12 0 mrt 0 0K 0K 78643K 3 0 ISOFS mount 1 32K 32K 78643K 1 0 MSDOSFS mount 1 16K 16K 78643K 1 0 ttys 43 201K 201K 78643K 43 0 exec 0 0K 1K 78643K 197 0 pagedep 1 8K 8K 78643K 1 0 inodedep 1 32K 32K 78643K 1 0 newblk 1 0K 0K 78643K 1 0 VM swap 7 26K 26K 78643K 7 0 UVM amap 95 37K 39K 78643K 1314 0 UVM aobj 35 4K 4K 78643K 35 0 memdesc 1 4K 4K 78643K 1 0 crypto data 1 1K 1K 78643K 1 0 ip6_options 0 0K 0K 78643K 46 0 NDP 12 0K 0K 78643K 21 0 temp 104 3015K 3107K 78643K 4876 0 kqueue 3 4K 9K 78643K 22 0 SYN cache 2 16K 16K 78643K 2 0 ddb> show all pools Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle arp 64 9 0 1 1 0 1 1 0 8 0 rtpcb 80 31 0 29 1 0 1 1 0 8 0 rtentry 112 56 0 12 2 0 2 2 0 8 0 unpcb 120 387 0 378 1 0 1 1 0 8 0 syncache 264 4 0 4 1 1 0 1 0 8 0 tcpqe 32 43 0 43 1 1 0 1 0 8 0 tcpcb 544 78 0 74 1 0 1 1 0 8 0 ipq 40 7 0 7 1 0 1 1 0 8 1 ipqe 40 182 0 182 1 0 1 1 0 8 1 inpcb 280 310 0 300 2 0 2 2 0 8 1 rttmr 72 1 0 1 1 0 1 1 0 8 1 nd6 48 8 0 3 1 0 1 1 0 8 0 swfcl 56 2 0 0 1 0 1 1 0 8 0 ppxss 1128 1 0 1 1 0 1 1 0 8 1 art_heap8 4096 1 0 0 1 0 1 1 0 8 0 art_heap4 256 263 0 64 14 0 14 14 0 8 1 art_table 32 264 0 64 2 0 2 2 0 8 0 art_node 16 55 0 14 1 0 1 1 0 8 0 sysvmsgpl 40 14 0 11 1 0 1 1 0 8 0 semupl 112 1 0 1 1 1 0 1 0 8 0 semapl 112 28 0 18 1 0 1 1 0 8 0 shmpl 112 33 0 0 1 0 1 1 0 8 0 dirhash 1024 17 0 0 3 0 3 3 0 8 0 dino1pl 128 1690 0 290 46 0 46 46 0 8 0 ffsino 240 1690 0 290 83 0 83 83 0 8 0 nchpl 144 2163 0 553 60 0 60 60 0 8 0 uvmvnodes 72 1817 0 0 34 0 34 34 0 8 0 vnodes 208 1817 0 0 96 0 96 96 0 8 0 namei 1024 5520 0 5520 1 0 1 1 0 8 1 vcpupl 1984 1 0 0 1 0 1 1 0 8 0 vmpool 528 3 0 2 1 0 1 1 0 8 0 scxspl 192 6383 0 6382 1 0 1 1 0 8 0 plimitpl 152 28 0 21 1 0 1 1 0 8 0 sigapl 424 396 0 367 4 0 4 4 0 8 0 futexpl 56 4904 0 4904 1 0 1 1 0 8 1 knotepl 112 73 0 54 1 0 1 1 0 8 0 kqueuepl 144 47 0 45 1 0 1 1 0 8 0 pipelkpl 16 97 0 87 1 0 1 1 0 8 0 pipepl 120 194 0 175 1 0 1 1 0 8 0 fdescpl 432 380 0 367 2 0 2 2 0 8 0 filepl 120 2488 0 2393 4 0 4 4 0 8 1 lockfpl 104 26 0 25 1 0 1 1 0 8 0 lockfspl 48 12 0 11 1 0 1 1 0 8 0 sessionpl 112 17 0 7 1 0 1 1 0 8 0 pgrppl 48 17 0 7 1 0 1 1 0 8 0 ucredpl 96 180 0 173 1 0 1 1 0 8 0 zombiepl 144 367 0 367 1 0 1 1 0 8 1 processpl 896 396 0 367 4 0 4 4 0 8 0 procpl 624 636 0 600 4 0 4 4 0 8 0 sosppl 128 1 0 1 1 0 1 1 0 8 1 sockpl 400 738 0 720 6 0 6 6 0 8 3 mcl64k 65536 32 0 28 1 0 1 1 0 8 0 mcl12k 12288 5 0 5 1 0 1 1 0 8 1 mcl9k 9216 3 0 3 1 1 0 1 0 8 0 mcl8k 8192 7 0 7 1 0 1 1 0 8 1 mcl4k 4096 26 0 26 2 1 1 1 0 8 1 mcl2k2 2112 1 0 1 1 0 1 1 0 8 1 mcl2k 2048 65240 0 65191 16 9 7 15 0 8 0 mtagpl 80 25 0 2 2 1 1 1 0 8 0 mbufpl 256 105346 0 104838 38 5 33 35 0 8 0 bufpl 280 4266 0 161 294 0 294 294 0 8 0 anonpl 16 51870 0 35428 84 2 82 82 0 107 14 amapchunkpl 152 1853 0 1710 17 1 16 16 0 158 10 amappl16 192 2004 0 1112 57 4 53 57 0 8 8 amappl15 184 192 0 189 1 0 1 1 0 8 0 amappl14 176 4 0 3 2 1 1 1 0 8 0 amappl13 168 24 0 23 1 0 1 1 0 8 0 amappl12 160 4 0 3 2 1 1 1 0 8 0 amappl11 152 65 0 52 1 0 1 1 0 8 0 amappl10 144 16 0 12 1 0 1 1 0 8 0 amappl9 136 375 0 372 1 0 1 1 0 8 0 amappl8 128 267 0 250 1 0 1 1 0 8 0 amappl7 120 115 0 102 1 0 1 1 0 8 0 amappl6 112 21 0 19 2 1 1 1 0 8 0 amappl5 104 321 0 310 1 0 1 1 0 8 0 amappl4 96 434 0 404 1 0 1 1 0 8 0 amappl3 88 114 0 108 1 0 1 1 0 8 0 amappl2 80 2342 0 2283 3 1 2 3 0 8 0 amappl1 72 16407 0 16022 27 18 9 20 0 8 0 amappl 80 864 0 821 2 0 2 2 0 84 0 dma4096 4096 1 0 1 1 1 0 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 64 34 0 0 1 0 1 1 0 8 0 uaddrrnd 24 383 0 369 1 0 1 1 0 8 0 uaddrbest 32 2 0 0 1 0 1 1 0 8 0 uaddr 24 383 0 369 1 0 1 1 0 8 0 vmmpekpl 168 6420 0 6390 2 0 2 2 0 8 0 vmmpepl 168 51994 0 50165 123 15 108 115 0 357 23 vmsppl 272 382 0 369 2 0 2 2 0 8 1 pdppl 4096 772 0 739 6 1 5 6 0 8 0 pvpl 32 165313 0 145976 194 0 194 194 0 265 35 pmappl 200 382 0 369 1 0 1 1 0 8 0 extentpl 40 46 0 29 1 0 1 1 0 8 0 phpool 112 181 0 18 5 0 5 5 0 8 0