panic: Data modified on freelist: word 4 of object 0xffff8000009d7000 size 0xe10 previous type free (0x0 != 0xdeaf4152) Stopped at db_enter+0x18: addq $0x8,%rsp TID PID UID PRFLAGS PFLAGS CPU COMMAND * 84685 83679 0 0x2 0 0K syz-executor.0 419208 63957 0 0x2 0x4000000 1 syz-fuzzer db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398 panic(ffffffff821f5e43) at panic+0x15c sys/kern/subr_prf.c:207 malloc(e10,27,9) at malloc+0xa23 sys/kern/kern_malloc.c:331 fdcopy(ffff800020ec9b00) at fdcopy+0x1fa sys/kern/kern_descrip.c:1135 process_new(ffff800020e929d8,ffff800020ec9b00,1) at process_new+0x12c sys/kern/kern_fork.c:253 fork1(ffff800020e6c758,1,ffffffff81e1e3b0,0,ffff800020f6b130,0) at fork1+0x31b sys/kern/kern_fork.c:377 syscall(ffff800020f6b1b0) at syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] syscall(ffff800020f6b1b0) at syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x7f7fffff1b70, 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{0}> ddb{0}> set $lines = 0 ddb{0}> set $maxwidth = 0 ddb{0}> show panic Data modified on freelist: word 4 of object 0xffff8000009d7000 size 0xe10 previous type free (0x0 != 0xdeaf4152) ddb{0}> trace db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398 panic(ffffffff821f5e43) at panic+0x15c sys/kern/subr_prf.c:207 malloc(e10,27,9) at malloc+0xa23 sys/kern/kern_malloc.c:331 fdcopy(ffff800020ec9b00) at fdcopy+0x1fa sys/kern/kern_descrip.c:1135 process_new(ffff800020e929d8,ffff800020ec9b00,1) at process_new+0x12c sys/kern/kern_fork.c:253 fork1(ffff800020e6c758,1,ffffffff81e1e3b0,0,ffff800020f6b130,0) at fork1+0x31b sys/kern/kern_fork.c:377 syscall(ffff800020f6b1b0) at syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] syscall(ffff800020f6b1b0) at syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x7f7fffff1b70, count: -8 ddb{0}> show registers rdi 0 rsi 0x1 rbp 0xffff800020f6add0 rbx 0xffff800020f6ae80 rdx 0x8b rcx 0x2 rax 0x1 r8 0xffffffff81f3c28f kprintf+0x16f r9 0x1 r10 0x2 r11 0x590321589b1e6cb7 r12 0x3000000008 r13 0xffff800020f6ade0 r14 0x100 r15 0x1 rip 0xffffffff8149f5a8 db_enter+0x18 cs 0x8 rflags 0x246 rsp 0xffff800020f6adc0 ss 0x10 db_enter+0x18: addq $0x8,%rsp ddb{0}> show proc PROC (syz-executor.0) pid=84685 stat=onproc flags process=2 proc=0 pri=78, usrpri=78, nice=20 forw=0xffffffffffffffff, list=0xffff800020e6cc38,0xffff800020e93888 process=0xffff800020ec9b00 user=0xffff800020f66000, vmspace=0xfffffd807efffcf0 estcpu=36, cpticks=7, pctcpu=0.24 user=0, sys=2, intr=0 ddb{0}> ps PID TID PPID UID S FLAGS WAIT COMMAND 88696 457489 0 0 3 0x14280 nfsidl nfsio 5550 480626 0 0 3 0x14280 nfsidl nfsio 51593 489497 0 0 3 0x14280 nfsidl nfsio 15779 39639 0 0 3 0x14280 nfsidl nfsio 7684 207121 0 0 3 0x14280 nfsidl nfsio 81794 202327 0 0 3 0x14280 nfsidl nfsio 63255 137976 0 0 3 0x14280 nfsidl nfsio 43702 160956 0 0 3 0x14280 nfsidl nfsio 14529 464600 0 0 3 0x14280 nfsidl nfsio 19953 161141 0 0 3 0x14280 nfsidl nfsio 69335 45620 0 0 3 0x14280 nfsidl nfsio 95533 67601 0 0 3 0x14280 nfsidl nfsio 1773 223175 0 0 3 0x14280 nfsidl nfsio 52938 157846 0 0 3 0x14280 nfsidl nfsio 95581 16793 0 0 3 0x14280 nfsidl nfsio 46043 220120 0 0 3 0x14280 nfsidl nfsio 81608 460845 0 0 3 0x14280 nfsidl nfsio 11512 96565 0 0 3 0x14280 nfsidl nfsio 15898 371835 0 0 3 0x14280 nfsidl nfsio 36310 56019 0 0 3 0x14280 nfsidl nfsio 34256 274945 0 0 3 0x14200 bored sosplice 1289 514990 63957 0 3 0x82 piperd syz-executor.1 *83679 84685 63957 0 7 0x2 syz-executor.0 63957 485527 18588 0 3 0x82 kqread syz-fuzzer 63957 447593 18588 0 3 0x4000082 nanosleep syz-fuzzer 63957 421724 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 132969 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 358776 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 319494 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 177625 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 274348 18588 0 3 0x4000082 thrsleep syz-fuzzer 63957 419208 18588 0 7 0x4000002 syz-fuzzer 63957 279351 18588 0 3 0x4000082 thrsleep syz-fuzzer 18588 241951 88017 0 3 0x10008a pause ksh 88017 405284 56050 0 3 0x92 select sshd 21469 478791 1 0 3 0x100083 ttyin getty 56050 197792 1 0 3 0x80 select sshd 62277 197262 41300 74 3 0x100092 bpf pflogd 41300 193707 1 0 3 0x80 netio pflogd 55514 121373 11390 73 3 0x100090 kqread syslogd 11390 392648 1 0 3 0x100082 netio syslogd 25289 365690 1 77 3 0x100090 poll dhclient 59768 47915 1 0 3 0x80 poll dhclient 26728 465666 0 0 3 0x14200 bored smr 27439 41579 0 0 2 0x14200 zerothread 83041 108047 0 0 3 0x14200 aiodoned aiodoned 12502 449573 0 0 3 0x14200 syncer update 88326 72357 0 0 3 0x14200 cleaner cleaner 18917 123567 0 0 3 0x14200 reaper reaper 22758 452364 0 0 3 0x14200 pgdaemon pagedaemon 21750 255139 0 0 3 0x14200 bored crynlk 54265 80914 0 0 3 0x14200 bored crypto 98093 470158 0 0 3 0x40014200 acpi0 acpi0 84643 205664 0 0 3 0x40014200 idle1 27755 301333 0 0 3 0x14200 bored softnet 14390 90602 0 0 3 0x14200 bored systqmp 13142 369477 0 0 3 0x14200 bored systq 73950 176054 0 0 3 0x40014200 bored softclock 16238 204979 0 0 3 0x40014200 idle0 1 13534 0 0 3 0x82 wait init 0 0 -1 0 3 0x10200 scheduler swapper ddb{0}> show all locks CPU 0: exclusive mutex /syzkaller/managers/multicore/kernel/sys/kern/kern_malloc.c:104 r = 0 (0xffffffff824a2390) #0 witness_lock+0x4c7 stacktrace_save sys/sys/stacktrace.h:36 [inline] #0 witness_lock+0x4c7 sys/kern/subr_witness.c:1164 #1 mtx_enter_try+0x102 #2 mtx_enter+0x4b sys/kern/kern_lock.c:266 #3 malloc+0x23b sys/kern/kern_malloc.c:209 #4 fdcopy+0x1fa sys/kern/kern_descrip.c:1135 #5 process_new+0x12c sys/kern/kern_fork.c:253 #6 fork1+0x31b sys/kern/kern_fork.c:377 #7 syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] #7 syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 #8 Xsyscall+0x128 Process 83679 (syz-executor.0) thread 0xffff800020e6c758 (84685) exclusive rwlock fdlock r = 0 (0xfffffd807cf85068) #0 witness_lock+0x4c7 stacktrace_save sys/sys/stacktrace.h:36 [inline] #0 witness_lock+0x4c7 sys/kern/subr_witness.c:1164 #1 fdcopy+0x131 sys/kern/kern_descrip.c:1111 #2 process_new+0x12c sys/kern/kern_fork.c:253 #3 fork1+0x31b sys/kern/kern_fork.c:377 #4 syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] #4 syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 #5 Xsyscall+0x128 exclusive kernel_lock &kernel_lock r = 0 (0xffffffff8266d5a0) #0 witness_lock+0x4c7 stacktrace_save sys/sys/stacktrace.h:36 [inline] #0 witness_lock+0x4c7 sys/kern/subr_witness.c:1164 #1 syscall+0x400 mi_syscall sys/sys/syscall_mi.h:93 [inline] #1 syscall+0x400 sys/arch/amd64/amd64/trap.c:570 #2 Xsyscall+0x128 exclusive mutex /syzkaller/managers/multicore/kernel/sys/kern/kern_malloc.c:104 r = 0 (0xffffffff824a2390) #0 witness_lock+0x4c7 stacktrace_save sys/sys/stacktrace.h:36 [inline] #0 witness_lock+0x4c7 sys/kern/subr_witness.c:1164 #1 mtx_enter_try+0x102 #2 mtx_enter+0x4b sys/kern/kern_lock.c:266 #3 malloc+0x23b sys/kern/kern_malloc.c:209 #4 fdcopy+0x1fa sys/kern/kern_descrip.c:1135 #5 process_new+0x12c sys/kern/kern_fork.c:253 #6 fork1+0x31b sys/kern/kern_fork.c:377 #7 syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] #7 syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 #8 Xsyscall+0x128 ddb{0}> show malloc Type InUse MemUse HighUse Limit Requests Type Lim devbuf 9527 6419K 7190K 78643K 11980 0 pcb 13 8K 8K 78643K 77 0 rtable 83 2K 3K 78643K 271 0 ifaddr 83 16K 16K 78643K 105 0 counters 43 33K 34K 78643K 47 0 ioctlops 0 0K 4K 78643K 1483 0 iov 0 0K 32K 78643K 77 0 mount 1 1K 1K 78643K 1 0 vnodes 1224 77K 77K 78643K 1582 0 UFS quota 1 32K 32K 78643K 1 0 UFS mount 5 36K 36K 78643K 5 0 shm 2 1K 5K 78643K 3 0 VM map 2 1K 1K 78643K 2 0 sem 11 1K 1K 78643K 17 0 dirhash 12 2K 2K 78643K 12 0 ACPI 1824 197K 290K 78643K 13058 0 file desc 4 13K 25K 78643K 333 0 sigio 0 0K 0K 78643K 5 0 proc 61 63K 95K 78643K 478 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 14 0 in_multi 60 3K 3K 78643K 89 0 ether_multi 1 0K 0K 78643K 10 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 49 228K 228K 78643K 49 0 exec 0 0K 1K 78643K 240 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 116 22K 39K 78643K 1959 0 UVM aobj 11 2K 3K 78643K 15 0 memdesc 1 4K 4K 78643K 1 0 crypto data 1 1K 1K 78643K 1 0 ip6_options 0 0K 0K 78643K 48 0 NDP 13 0K 0K 78643K 20 0 temp 111 3036K 3100K 78643K 10489 0 kqueue 3 4K 10K 78643K 16 0 SYN cache 2 16K 16K 78643K 2 0 ddb{0}> show all pools Name Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle arp 64 7 0 1 1 0 1 1 0 8 0 plcache 128 20 0 0 1 0 1 1 0 8 0 rtpcb 80 40 0 38 1 0 1 1 0 8 0 rtentry 112 54 0 21 2 0 2 2 0 8 0 unpcb 120 273 0 263 1 0 1 1 0 8 0 syncache 264 4 0 4 1 1 0 1 0 8 0 tcpqe 32 543 0 543 1 1 0 1 0 8 0 tcpcb 544 107 0 103 1 0 1 1 0 8 0 inpcb 280 340 0 333 4 2 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 pkpcb 40 3 0 3 2 1 1 1 0 8 1 pffrag 232 5 0 5 3 3 0 1 0 482 0 pffrnode 88 5 0 5 3 3 0 1 0 8 0 pffrent 40 139 0 139 3 3 0 1 0 8 0 pfosfp 40 846 0 423 5 0 5 5 0 8 0 pfosfpen 112 1428 0 714 21 0 21 21 0 8 0 pfstitem 24 42 0 9 1 0 1 1 0 8 0 pfstkey 112 42 0 9 1 0 1 1 0 8 0 pfstate 328 42 0 9 3 0 3 3 0 8 0 pfrule 1360 21 0 16 2 1 1 2 0 8 0 art_heap8 4096 1 0 0 1 0 1 1 0 8 0 art_heap4 256 258 0 83 12 1 11 12 0 8 0 art_table 32 259 0 83 2 0 2 2 0 8 0 art_node 16 53 0 26 1 0 1 1 0 8 0 sysvmsgpl 40 10 0 3 1 0 1 1 0 8 0 semupl 112 3 0 3 2 2 0 1 0 8 0 semapl 112 9 0 0 1 0 1 1 0 8 0 shmpl 112 13 0 4 1 0 1 1 0 8 0 dirhash 1024 17 0 0 3 0 3 3 0 8 0 dino2pl 256 1861 0 457 89 0 89 89 0 8 0 ffsino 272 1861 0 457 95 1 94 94 0 8 0 nchpl 144 2607 0 1000 60 0 60 60 0 8 0 uvmvnodes 72 2214 0 0 41 0 41 41 0 8 0 vnodes 208 2214 0 0 117 0 117 117 0 8 0 namei 1024 7174 0 7174 2 1 1 1 0 8 1 percpumem 16 34 0 2 1 0 1 1 0 8 0 vmpool 560 2 0 2 1 0 1 1 0 8 1 scxspl 192 7217 0 7217 10 7 3 7 0 8 3 plimitpl 152 23 0 15 1 0 1 1 0 8 0 sigapl 424 569 0 518 6 0 6 6 0 8 0 futexpl 56 5591 0 5591 1 0 1 1 0 8 1 knotepl 112 78 0 59 1 0 1 1 0 8 0 kqueuepl 144 42 0 40 1 0 1 1 0 8 0 pipelkpl 48 127 0 117 1 0 1 1 0 8 0 pipepl 120 254 0 235 1 0 1 1 0 8 0 fdescpl 496 534 0 518 3 0 3 3 0 8 0 filepl 152 3370 0 3270 7 1 6 6 0 8 2 lockfpl 104 163 0 162 1 0 1 1 0 8 0 lockfspl 48 51 0 50 1 0 1 1 0 8 0 sessionpl 112 18 0 7 1 0 1 1 0 8 0 pgrppl 48 22 0 11 1 0 1 1 0 8 0 ucredpl 96 260 0 251 1 0 1 1 0 8 0 zombiepl 144 518 0 518 2 1 1 1 0 8 1 processpl 984 570 0 518 8 1 7 7 0 8 0 procpl 624 1211 0 1150 6 0 6 6 0 8 1 sosppl 128 5 0 5 2 1 1 1 0 8 1 sockpl 400 661 0 642 7 2 5 5 0 8 3 mcl64k 65536 8 0 0 1 0 1 1 0 8 0 mcl12k 12288 4 0 0 1 0 1 1 0 8 0 mcl9k 9216 1 0 0 1 0 1 1 0 8 0 mcl8k 8192 3 0 0 1 0 1 1 0 8 0 mcl4k 4096 7 0 0 1 0 1 1 0 8 0 mcl2k2 2112 2 0 0 1 0 1 1 0 8 0 mcl2k 2048 233 0 0 29 1 28 29 0 8 0 mtagpl 80 184 0 0 4 0 4 4 0 8 0 mbufpl 256 520 0 0 30 0 30 30 0 8 0 bufpl 280 4174 0 137 289 0 289 289 0 8 0 anonpl 16 63617 0 49072 77 16 61 75 0 124 1 amapchunkpl 152 2829 0 2702 18 5 13 13 0 158 7 amappl16 192 2459 0 1672 52 11 41 52 0 8 0 amappl15 184 69 0 67 1 0 1 1 0 8 0 amappl14 176 22 0 18 1 0 1 1 0 8 0 amappl13 168 262 0 257 1 0 1 1 0 8 0 amappl12 160 8 0 6 2 1 1 1 0 8 0 amappl11 152 57 0 42 1 0 1 1 0 8 0 amappl10 144 29 0 23 1 0 1 1 0 8 0 amappl9 136 377 0 375 1 0 1 1 0 8 0 amappl8 128 355 0 317 2 0 2 2 0 8 0 amappl7 120 117 0 107 1 0 1 1 0 8 0 amappl6 112 26 0 20 1 0 1 1 0 8 0 amappl5 104 451 0 436 1 0 1 1 0 8 0 amappl4 96 716 0 687 1 0 1 1 0 8 0 amappl3 88 112 0 107 1 0 1 1 0 8 0 amappl2 80 3343 0 3282 2 0 2 2 0 8 0 amappl1 72 21107 0 20675 24 14 10 18 0 8 0 amappl 80 1434 0 1394 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 14 0 4 1 0 1 1 0 8 0 uaddrrnd 24 535 0 520 1 0 1 1 0 8 0 uaddrbest 32 2 0 0 1 0 1 1 0 8 0 uaddr 24 535 0 520 1 0 1 1 0 8 0 vmmpekpl 168 7950 0 7917 2 0 2 2 0 8 0 vmmpepl 168 71095 0 69257 119 31 88 108 0 357 0 vmsppl 368 534 0 520 2 0 2 2 0 8 0 pdppl 4096 1078 0 1040 6 0 6 6 0 8 0 pvpl 32 203581 0 185864 184 16 168 182 0 265 22 pmappl 232 534 0 520 2 1 1 2 0 8 0 extentpl 40 53 0 36 1 0 1 1 0 8 0 phpool 112 290 0 9 9 0 9 9 0 8 0 ddb{0}> machine ddbcpu 0 Invalid cpu 0 ddb{0}> trace db_enter() at db_enter+0x18 sys/arch/amd64/amd64/db_interface.c:398 panic(ffffffff821f5e43) at panic+0x15c sys/kern/subr_prf.c:207 malloc(e10,27,9) at malloc+0xa23 sys/kern/kern_malloc.c:331 fdcopy(ffff800020ec9b00) at fdcopy+0x1fa sys/kern/kern_descrip.c:1135 process_new(ffff800020e929d8,ffff800020ec9b00,1) at process_new+0x12c sys/kern/kern_fork.c:253 fork1(ffff800020e6c758,1,ffffffff81e1e3b0,0,ffff800020f6b130,0) at fork1+0x31b sys/kern/kern_fork.c:377 syscall(ffff800020f6b1b0) at syscall+0x4a4 mi_syscall sys/sys/syscall_mi.h:102 [inline] syscall(ffff800020f6b1b0) at syscall+0x4a4 sys/arch/amd64/amd64/trap.c:570 Xsyscall() at Xsyscall+0x128 end of kernel end trace frame: 0x7f7fffff1b70, count: -8 ddb{0}> machine ddbcpu 1 Stopped at x86_ipi_db+0x1a: addq $0x8,%rsp x86_ipi_db(ffff800020e00ff0) at x86_ipi_db+0x1a sys/arch/amd64/amd64/db_interface.c:352 x86_ipi_handler() at x86_ipi_handler+0xc6 sys/arch/amd64/amd64/ipi.c:106 Xresume_lapic_ipi() at Xresume_lapic_ipi+0x23 end of kernel end trace frame: 0xc0003eec58, count: 12 ddb{1}> trace x86_ipi_db(ffff800020e00ff0) at x86_ipi_db+0x1a sys/arch/amd64/amd64/db_interface.c:352 x86_ipi_handler() at x86_ipi_handler+0xc6 sys/arch/amd64/amd64/ipi.c:106 Xresume_lapic_ipi() at Xresume_lapic_ipi+0x23 end of kernel end trace frame: 0xc0003eec58, count: -3