KASAN: invalid memory access in free

Status: closed as invalid on 2026/07/30 09:17
Reported-by: syzbot+fba1aeba133a4760690b@syzkaller.appspotmail.com
First crash: 51d, last: 51d

Sample crash report:
panic: Caught invalid memory access at ffff800001b4d0e8 size 8 op 1
Stopped at      db_enter+0x17:  popq    %rbp
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
 428762  79573      0           0        0x1    0  syz-executor
*337144   6461      0         0x2        0x1    1  syz-executor
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff846334c7) at panic+0x270 sys/kern/subr_prf.c:198
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 kasan_shadow_check sys/kern/subr_kasan.c:-1 [inline]
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 sys/kern/subr_kasan.c:1038
free(ffff800001b4d200,7f,18) at free+0x678 sys/kern/kern_malloc.c:556
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae x86_atomic_clearbits_u32 sys/arch/amd64/compile/SYZKALLER/obj/machine/atomic.h:-1 [inline]
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae sys/kern/kern_ktrace.c:186
syscall(ffff800029ad8db0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff800029ad8db0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f056732a4e0, count: 8
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: Caught invalid memory access at ffff800001b4d0e8 size 8 op 1
ddb{1}> trace
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff846334c7) at panic+0x270 sys/kern/subr_prf.c:198
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 kasan_shadow_check sys/kern/subr_kasan.c:-1 [inline]
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 sys/kern/subr_kasan.c:1038
free(ffff800001b4d200,7f,18) at free+0x678 sys/kern/kern_malloc.c:556
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae x86_atomic_clearbits_u32 sys/arch/amd64/compile/SYZKALLER/obj/machine/atomic.h:-1 [inline]
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae sys/kern/kern_ktrace.c:186
syscall(ffff800029ad8db0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff800029ad8db0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f056732a4e0, count: -7
ddb{1}> show registers
rdi                                0
rsi                              0x1
rbp               0xffff800029ad8850
rbx               0xffff800029ad88c0
rdx                                0
rcx               0xffff800028ff3ff0
rax                                0
r8                 0x101010101010101
r9                0x8080808080808080
r10               0xffff800029ad8638
r11               0xffffffff814e1f30    x86_bus_space_io_read_1
r12               0xffffffff846334c7    db_machine_command_table+0x9b027
r13               0xffff800028ff4c08
r14               0xffff800028ff4e07
r15                              0x1
rip               0xffffffff81006567    db_enter+0x17
cs                               0x8
rflags                         0x246
rsp               0xffff800029ad8850
ss                              0x10
db_enter+0x17:  popq    %rbp
ddb{1}> show proc
PROC (syz-executor) tid=337144 pid=6461 tcnt=1 stat=onproc
    flags process=2<EXEC> proc=1<INKTR>
    runpri=32, usrpri=74, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff800029942fa8,0xffff8000298a4548
    process=0xffff800045ffab68 user=0xffff800029acd000, vmspace=0xffff800000d87000
    estcpu=24, cpticks=75, pctcpu=0.40, user=0, sys=73, intr=1
ddb{1}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
 15507  437008  20693      0  2           0                syz-executor
 15507   63237  20693      0  2   0x4000000                syz-executor
 79573  428762  92466      0  7         0x1                syz-executor
 22448  139632  24290      0  2           0                syz-executor
 22448  412951  24290      0  3   0x4000080  fsleep        syz-executor
 41704  436934  24551      0  2         0x2                syz-executor
 72170  471163  40732      0  3        0x80  nanoslp       syz-executor
 72170   21450  40732      0  3   0x4000088  kqpoll        syz-executor
 72170  440344  40732      0  3   0x4000080  fsleep        syz-executor
 22566   36441  45000      0  3        0x90  nanoslp       syz-executor
 22566   92896  45000      0  3   0x4000090  msgwait       syz-executor
 22566  276844  45000      0  3   0x4000090  fsleep        syz-executor
 45000   83215  24551      0  3        0x82  nanoslp       syz-executor
 81462  128388      1      0  3        0x82  nanoslp       getty
* 6461  337144  24551      0  7         0x3                syz-executor
 20693  395313  24551      0  3        0x82  nanoslp       syz-executor
 40732  450053  24551      0  3        0x82  nanoslp       syz-executor
 92466   24010  24551      0  3        0x82  nanoslp       syz-executor
   824  306386  24551      0  3        0x82  nanoslp       syz-executor
 24290  485568  24551      0  3        0x82  nanoslp       syz-executor
 24551  306910      1      0  3        0x82  kqread        syz-executor
 85144  104162      0      0  2  0x40014200                smr
 38464  292637      0      0  2     0x14200                zerothread
 66282  261703      0      0  3     0x14200  aiodoned      aiodoned
 75008  266703      0      0  3     0x14200  syncer        update
 16555  232068      0      0  3     0x14200  cleaner       cleaner
 22747  196155      0      0  3     0x14200  reaper        reaper
 14714  388220      0      0  3     0x14200  pgdaemon      pagedaemon
 18138  464546      0      0  3     0x14200  bored         viomb
 53854    4768      0      0  3  0x40014200  acpi0         acpi0
 26348  105954      0      0  3  0x40014200                idle1
 99210    5583      0      0  3     0x14200  bored         softnet1
 66772  222385      0      0  3     0x14200  bored         softnet0
 90023   36328      0      0  3     0x14200  smrbar        systqmp
 37156  121659      0      0  3     0x14200  bored         systq
 20024  215405      0      0  3     0x14200  tmoslp        softclockmp
 43827  111913      0      0  3  0x40014200  tmoslp        softclock
  6664  367748      0      0  3  0x40014200                idle0
     1  175063      0      0  3        0x82  wait          init
     0       0     -1      0  3     0x10200  scheduler     swapper
ddb{1}> show all locks
CPU 1:
exclusive mutex /syzkaller/managers/kasan/kernel/sys/kern/kern_malloc.c:109 r = 0 (0xffffffff85227630)
#0  witness_lock+0x632 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0  witness_lock+0x632 sys/kern/subr_witness.c:1160
#1  mtx_enter+0x683 sys/kern/kern_lock.c:487
#2  free+0x129 sys/kern/kern_malloc.c:441
#3  ktrsyscall+0x4ae x86_atomic_clearbits_u32 sys/arch/amd64/compile/SYZKALLER/obj/machine/atomic.h:-1 [inline]
#3  ktrsyscall+0x4ae sys/kern/kern_ktrace.c:186
#4  syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
#4  syscall+0x640 sys/arch/amd64/amd64/trap.c:783
#5  Xsyscall+0x128
Process 90023 (systqmp) thread 0xffff800045ffe000 (36328)
shared rwlock systqmp r = 0 (0xffffffff85403f18)
#0  witness_lock+0x632 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0  witness_lock+0x632 sys/kern/subr_witness.c:1160
#1  taskq_thread+0x1ba sys/kern/kern_task.c:442
#2  proc_trampoline+0x10
ddb{1}> show malloc
           Type InUse  MemUse  HighUse   Limit  Requests Type Lim
         devbuf 11046  12477K   12624K 166960K     12290        0
            pcb    17     28K      30K 166960K        49        0
         rtable   216     11K      13K 166960K       418        0
             pf    34     22K      24K 166960K        78        0
         ifaddr    40     11K      13K 166960K        60        0
        ifgroup    53      2K       2K 166960K        79        0
         sysctl     3      1K      13K 166960K         8        0
       counters    70     42K      43K 166960K        84        0
       ioctlops     0      0K       4K 166960K      1509        0
            iov     0      0K       8K 166960K        71        0
          mount     1      1K       1K 166960K         1        0
            log     2      0K       0K 166960K         6        0
         vnodes  1301     84K      84K 166960K      1487        0
      UFS quota     1     36K      36K 166960K         1        0
      UFS mount     5     44K      44K 166960K         5        0
            shm     2      2K      10K 166960K        17        0
         VM map     2      1K       1K 166960K         2        0
            sem     8      0K       1K 166960K         9        0
        dirhash    12      2K       2K 166960K        12        0
           ACPI  1692    195K     286K 166960K     12470        0
      file desc    16     61K      97K 166960K       332        0
          sigio     0      0K       0K 166960K         1        0
           proc    21     46K     177K 166960K       660        0
        subproc    64      8K       9K 166960K        91        0
    NFS srvsock     1      0K       0K 166960K         1        0
     NFS daemon     1     20K      20K 166960K         1        0
    ip_moptions     0      0K       0K 166960K         6        0
       in_multi    88      6K       7K 166960K       121        0
    ether_multi     1      0K       0K 166960K         1        0
            mrt     0      0K       0K 166960K        13        0
    ISOFS mount     1     36K      36K 166960K         1        0
  MSDOSFS mount     1     20K      20K 166960K         1        0
           ttys    61    425K     425K 166960K        61        0
           exec     0      0K       2K 166960K       421        0
   fusefs mount     1     36K      36K 166960K         1        0
            tdb     3      1K       1K 166960K         3        0
        VM swap     8     62K      64K 166960K        10        0
       UVM amap   122    127K     254K 166960K      4722        0
       UVM aobj    58      7K       7K 166960K        59        0
     pinsyscall    19     38K     108K 166960K      1548        0
        memdesc     1      4K       4K 166960K         1        0
    crypto data     1      1K       1K 166960K         1        0
    ip6_options     0      0K       0K 166960K         1        0
            NDP    12      0K       1K 166960K        39        0
           temp    36   9171K    9491K 166960K     10678        0
         kqueue     2      8K      45K 166960K        46        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       28    0        0     1     0     1     1     0     8    0
rtpcb      120       38    0       38     1     0     1     1     0     8    1
rtentry    176      135    0       36     6     0     6     6     0     8    0
unpcb      144      305    0      305     6     0     6     6     0     8    6
syncache   336        4    0        4     2     2     0     1     0     8    0
tcpcb      736       55    0       54     4     0     4     4     0     8    3
arp        136       22    0        6     1     0     1     1     0     8    0
inpcb      328      237    0      236     6     0     6     6     0     8    5
nd6        152       32    0       11     1     0     1     1     0     8    0
kcovpl      48       10    0        3     1     0     1     1     0     8    0
ppxss      1192       3    0        2     1     0     1     1     0     8    0
pffrag     232        1    0        0     1     0     1     1     0   482    0
pffrnode    88        1    0        0     1     0     1     1     0     8    0
pffrent     40        1    0        0     1     0     1     1     0     8    0
pfosfp      40     1428    0     1005     5     0     5     5     0     8    0
pfosfpen   112     1428    0      714    21     0    21    21     0     8    0
pfrktable  1344       1    0        1     1     0     1     1     0     8    1
pftag       88        2    0        0     1     0     1     1     0     8    0
pfstitem    24       33    0        0     1     0     1     1     0     8    0
pfstkey    128       33    0        0     2     0     2     2     0     8    0
pfstate    448       33    0        0     4     0     4     4     0     8    0
pfrule     1360      25    0       20     2     1     1     2     0     8    0
art_heap8  4096       1    0        0     1     0     1     1     0     8    0
art_heap4  256      546    0       90    29     0    29    29     0     8    0
art_table   40      547    0       90     5     0     5     5     0     8    0
art_node    32      135    0       45     1     0     1     1     0     8    0
sysvmsgpl   40       35    0       34     1     0     1     1     0     8    0
semupl     112        1    0        1     1     1     0     1     0     8    0
semapl      72        6    0        0     1     0     1     1     0     8    0
shmpl      112       56    0        1     2     0     2     2     0     8    0
dirhash    1024      17    0        0     3     0     3     3     0     8    0
dino2pl    256     1822    0      345    93     0    93    93     0     8    0
ffsino     296     1822    0      345   114     0   114   114     0     8    0
nchpl      144     2240    0      532    64     0    64    64     0     8    0
vnodes     216     2005    0        0   112     0   112   112     0     8    0
namei      1024    7119    0     7119     2     1     1     2     0     8    1
percpumem   16       58    0        7     1     0     1     1     0     8    0
kstatmem   264       41    0       14     2     0     2     2     0     8    0
scxspl     216     8225    0     8225     6     4     2     3     1     8    2
plimitpl   152       41    0       31     1     0     1     1     0     8    0
sigapl     424      645    0      610     7     1     6     7     0     8    1
knotepl    120       61    0        0     2     0     2     2     0     8    0
kqueuepl   224       61    0       59     1     0     1     1     0     8    0
pipepl     344      191    0      164     6     0     6     6     0     8    3
fdescpl    528      629    0      610     3     0     3     3     0     8    0
filepl     160     2786    0     2639    15     0    15    15     0     8    6
lockfpl    104       65    0       65     1     0     1     1     0     8    1
lockfspl    48       32    0       32     1     0     1     1     0     8    1
sessionpl  144       35    0       33     1     0     1     1     0     8    0
pgrppl      48       50    0       40     1     0     1     1     0     8    0
ucredpl    104      292    0      288     1     0     1     1     0     8    0
zombiepl   144      612    0      610     1     0     1     1     0     8    0
processpl  1232     645    0      610     5     1     4     5     0     8    0
procpl     664      906    0      865     6     0     6     6     0     8    1
sosppl     176        2    0        2     1     0     1     1     0     8    1
sockpl     752      581    0      580    16     7     9    16     0     8    8
mcl64k     65536      2    0        0     1     0     1     1     0     8    0
mcl16k     16384      1    0        0     1     0     1     1     0     8    0
mcl12k     12288      1    0        0     1     0     1     1     0     8    0
mcl9k128   9344       1    0        0     1     0     1     1     0     8    0
mcl8k      8192       3    0        0     1     0     1     1     0     8    0
mcl4k      4096     111    0        0    14     0    14    14     0     8    0
mcl2k      2048      21    0        0     3     0     3     3     0     8    0
mextrefs    64       19    0        0     1     0     1     1     0     8    0
mtagpl      96        2    0        0     1     0     1     1     0     8    0
mbufpl     256      185    0        0    12     0    12    12     0     8    0
bufpl      272     2670    0      105   171     0   171   171     0     8    0
anonpl      32     4389    0        0    37     1    36    37     0   222    0
amapchunkpl 152   13797    0    13480    23     0    23    23     0   158    5
amappl16   200     2127    0     2112     5     3     2     5     0     8    0
amappl15   192        2    0        2     1     1     0     1     0     8    0
amappl14   184      457    0      457     1     0     1     1     0     8    1
amappl13   176      130    0      129     1     0     1     1     0     8    0
amappl12   168      891    0      874     2     0     2     2     0     8    0
amappl11   160       10    0       10     2     1     1     1     0     8    1
amappl10   152       69    0       69     1     0     1     1     0     8    1
amappl9    144      272    0      272     1     0     1     1     0     8    1
amappl8    136      109    0      109     1     0     1     1     0     8    1
amappl7    128      157    0      155     1     0     1     1     0     8    0
amappl6    120      178    0      178     1     0     1     1     0     8    1
amappl5    112      114    0      114     1     0     1     1     0     8    1
amappl4    104      324    0      321     1     0     1     1     0     8    0
amappl3     96     2617    0     2546     4     0     4     4     0     8    1
amappl2     88      562    0      554     2     0     2     2     0     8    0
amappl1     80    11483    0    11367    15     2    13    15     0     8    8
amappl      88     3922    0     3815     5     0     5     5     0    92    0
uvmvnodes   80      103    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       58    0        1     2     0     2     2     0     8    0
uaddrrnd    24      629    0      610     1     0     1     1     0     8    0
uaddrbest   32        2    0        0     1     0     1     1     0     8    0
uaddr       24      629    0      610     1     0     1     1     0     8    0
vmmpekpl   168     7326    0     7289     3     0     3     3     0     8    0
vmmpepl    168    49084    0    48276    87     0    87    87     0   357   46
vmsppl     488      628    0      610     5     0     5     5     0     8    1
rwobjpl     80    16963    0    16512    25     2    23    25     0     8    2
pdppl      4096    1267    0     1220   101    50    51    89     0     8    4
pvpl        32    10716    0        0    88     1    87    87     0   265    0
pmappl     256      628    0      610     3     0     3     3     0     8    0
extentpl    40       45    0       27     1     0     1     1     0     8    0
phpool     112      450    0       56    12     0    12    12     0     8    0
ddb{1}> machine ddbcpu 0
Stopped at      x86_ipi_db+0x19:        leave
x86_ipi_db(ffffffff853a2ff0) at x86_ipi_db+0x19 sys/arch/amd64/amd64/db_interface.c:412
x86_ipi_handler() at x86_ipi_handler+0x112 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
mtx_enter(ffffffff85227620) at mtx_enter+0x467 sys/kern/kern_lock.c:454
malloc(10,7f,1) at malloc+0x2a5 sys/kern/kern_malloc.c:217
ktrsyscall(ffff800029942a78,c,8,ffff80002999bab0) at ktrsyscall+0x201 sys/kern/kern_ktrace.c:174
syscall(ffff80002999bab0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff80002999bab0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x72cd72455d70, count: 7
ddb{0}> trace
x86_ipi_db(ffffffff853a2ff0) at x86_ipi_db+0x19 sys/arch/amd64/amd64/db_interface.c:412
x86_ipi_handler() at x86_ipi_handler+0x112 sys/arch/amd64/amd64/ipi.c:106
Xresume_lapic_ipi() at Xresume_lapic_ipi+0x27
mtx_enter(ffffffff85227620) at mtx_enter+0x467 sys/kern/kern_lock.c:454
malloc(10,7f,1) at malloc+0x2a5 sys/kern/kern_malloc.c:217
ktrsyscall(ffff800029942a78,c,8,ffff80002999bab0) at ktrsyscall+0x201 sys/kern/kern_ktrace.c:174
syscall(ffff80002999bab0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff80002999bab0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x72cd72455d70, count: -8
ddb{0}> machine ddbcpu 1
Stopped at      db_enter+0x17:  popq    %rbp
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff846334c7) at panic+0x270 sys/kern/subr_prf.c:198
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 kasan_shadow_check sys/kern/subr_kasan.c:-1 [inline]
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 sys/kern/subr_kasan.c:1038
free(ffff800001b4d200,7f,18) at free+0x678 sys/kern/kern_malloc.c:556
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae x86_atomic_clearbits_u32 sys/arch/amd64/compile/SYZKALLER/obj/machine/atomic.h:-1 [inline]
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae sys/kern/kern_ktrace.c:186
syscall(ffff800029ad8db0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff800029ad8db0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f056732a4e0, count: 8
ddb{1}> trace
db_enter() at db_enter+0x17 sys/arch/amd64/amd64/db_interface.c:457
panic(ffffffff846334c7) at panic+0x270 sys/kern/subr_prf.c:198
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 kasan_shadow_check sys/kern/subr_kasan.c:-1 [inline]
__asan_store8_noabort(ffff800001b4d0e8) at __asan_store8_noabort+0xe4 sys/kern/subr_kasan.c:1038
free(ffff800001b4d200,7f,18) at free+0x678 sys/kern/kern_malloc.c:556
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae x86_atomic_clearbits_u32 sys/arch/amd64/compile/SYZKALLER/obj/machine/atomic.h:-1 [inline]
ktrsyscall(ffff800029942548,57,10,ffff800029ad8db0) at ktrsyscall+0x4ae sys/kern/kern_ktrace.c:186
syscall(ffff800029ad8db0) at syscall+0x640 mi_syscall sys/sys/syscall_mi.h:154 [inline]
syscall(ffff800029ad8db0) at syscall+0x640 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f056732a4e0, count: -7
ddb{1}> 

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/11 02:07 https://github.com/blackgnezdo/openbsd-src.git syzbot-kasan 275dedaf93b0 d78ea535 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-kasan KASAN: invalid memory access in free
* Struck through repros no longer work on HEAD.