syzbot


uvm_fault: sys_shmat (3)

Status: upstream: reported on 2026/06/24 23:01
Reported-by: syzbot+f5d2ec16c4993e11ed9e@syzkaller.appspotmail.com
First crash: 13d, last: 1d12h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
openbsd uvm_fault: sys_shmat (2) -1 7 111d 280d 0/4 auto-obsoleted due to no activity on 2026/06/17 15:49
openbsd uvm_fault: sys_shmat -1 1 375d 375d 0/4 auto-obsoleted due to no activity on 2025/09/26 10:39

Sample crash report:
uvm_fault(0xfffff50069c859a8, 0x0, 0, 1) -> e
kernel: page fault trap, code=0
Stopped at      sys_shmat+0x453:        movq    0(%r15),%rdi
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
  90393  27822      0           0          0    0  syz-executor
*379098  86586      0           0  0x4000000    1K syz-executor
sys_shmat(ffff800045fefca0,ffff80003a3a3b70,ffff80003a3a3ac0) at sys_shmat+0x453 sys/kern/sysv_shm.c:290
syscall(ffff80003a3a3b70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003a3a3b70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f1222a96e0, count: 12
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: uvm_fault(0xfffff50069c859a8, 0x0, 0, 1) -> e
ddb{1}> trace
sys_shmat(ffff800045fefca0,ffff80003a3a3b70,ffff80003a3a3ac0) at sys_shmat+0x453 sys/kern/sysv_shm.c:290
syscall(ffff80003a3a3b70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003a3a3b70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f1222a96e0, count: -3
ddb{1}> show registers
rdi                                0
rsi                                0
rbp               0xffff80003a3a3a90
rbx               0xfffff5006ca4fee0
rdx                                0
rcx                              0x1
rax                              0x1
r8                             0x180
r9                0xfffff500097fd3a8
r10                                0
r11               0x98c2606492d2da0c
r12               0xffff800045fefca0
r13               0xffff800001600010
r14                              0x3
r15                                0
rip               0xffffffff81bdaee3    sys_shmat+0x453
cs                               0x8
rflags                       0x10246    __ALIGN_SIZE+0xf246
rsp               0xffff80003a3a3a00
ss                              0x10
sys_shmat+0x453:        movq    0(%r15),%rdi
ddb{1}> show proc
PROC (syz-executor) tid=379098 pid=86586 tcnt=4 stat=onproc
    flags process=0 proc=4000000<THREAD>
    runpri=86, usrpri=86, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff800045fef4d8,0xffff80003c3b8560
    process=0xffff80003c3d79e0 user=0xffff80003a39e000, vmspace=0xfffff50069c859a8
    estcpu=36, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{1}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
 52239  199691  25446      0  2           0                syz-executor
 52239  174266  25446      0  2   0x4000000                syz-executor
 27822   90393  39716      0  7           0                syz-executor
 27822  307074  39716      0  3   0x4000080  fsleep        syz-executor
 27822  449835  39716      0  2   0x4000000                syz-executor
 38130  155594      1      0  3        0x82  nanoslp       getty
 78613  275995  77650      0  2           0                syz-executor
 78613  310499  77650      0  2   0x4000000                syz-executor
 78613   59325  77650      0  3   0x4000080  kqpoll        syz-executor
 78613  466460  77650      0  3   0x4000080  fsleep        syz-executor
 96156  229075  72249      0  3           0  kmmaplk       syz-executor
 96156  239201  72249      0  3   0x4000080  fsleep        syz-executor
 86586  184350  99440      0  2           0                syz-executor
 86586  515482  99440      0  2   0x4000000                syz-executor
*86586  379098  99440      0  7   0x4000000                syz-executor
 86586  224586  99440      0  2   0x4000000                syz-executor
  3972  301473  85862      0  3    0x100082  sbwait        ndp
 85862  157144  11388      0  3    0x10008a  sigsusp       sh
 96258   89274  82012      0  3        0x82  nanoslp       syz-executor
 25446  405212  82012      0  3        0x82  nanoslp       syz-executor
 77650  387818  82012      0  3        0x82  nanoslp       syz-executor
 39716  496106  82012      0  3        0x82  nanoslp       syz-executor
 99440  268308  82012      0  3        0x82  nanoslp       syz-executor
 72249  442276  82012      0  3        0x82  nanoslp       syz-executor
 11388  329609  82012      0  3        0x82  wait          syz-executor
 82012   93288  13875      0  3        0x82  wait          syz-executor
 13875  243829   9268      0  3    0x10008a  sigsusp       ksh
  9268  377727  41297      0  3        0x98  kqread        sshd-session
 41297  222788  65801      0  3        0x92  kqread        sshd-session
 65801  336056      1      0  3        0x88  kqread        sshd
 50218   14011  78438     74  3   0x1100092  bpf           pflogd
 78438  417805      1      0  3        0x80  sbwait        pflogd
 32231  143101  40520     73  3   0x1100090  kqread        syslogd
 40520  250119      1      0  3    0x100082  sbwait        syslogd
  2351  291334      1      0  3    0x100080  kqread        resolvd
 50896  443996   8641     77  3    0x100092  kqread        dhcpleased
 54355  257019   8641     77  3    0x100092  kqread        dhcpleased
  8641  225251      1      0  3        0x80  kqread        dhcpleased
 83983  215016      0      0  3     0x14200  bored         smr
 50800  325550      0      0  2     0x14200                zerothread
 13801  512873      0      0  3     0x14200  aiodoned      aiodoned
 76029  408977      0      0  3     0x14200  syncer        update
 45686  524245      0      0  3     0x14200  cleaner       cleaner
 68137  248319      0      0  3     0x14200  reaper        reaper
 26593  126966      0      0  3     0x14200  pgdaemon      pagedaemon
 47986  159915      0      0  3     0x14200  bored         viomb
 27959  395547      0      0  3  0x40014200  acpi0         acpi0
  9261  253974      0      0  3  0x40014200                idle1
 99841  108436      0      0  3     0x14200  bored         softnet1
 59651  247491      0      0  3     0x14200  bored         softnet0
 15789  249342      0      0  3     0x14200  smrbar        systqmp
 58882  341318      0      0  3     0x14200  bored         systq
 42396  159498      0      0  3     0x14200  tmoslp        softclockmp
 45108  165226      0      0  3  0x40014200  tmoslp        softclock
 42412  229966      0      0  3  0x40014200                idle0
     1  143670      0      0  3        0x82  wait          init
     0       0     -1      0  3     0x10200  scheduler     swapper
ddb{1}> show all locks
Process 27822 (syz-executor) thread 0xffff80003c3b6558 (449835)
exclusive rwlock vmmaplk r = 0 (0xfffff5006cbee6d0)
#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_read+0x3e8 sys/kern/kern_rwlock.c:413
#2  uvmfault_lookup+0x122 sys/uvm/uvm_fault.c:1880
#3  uvm_fault_check+0x4f sys/uvm/uvm_fault.c:693
#4  uvm_fault+0x106 sys/uvm/uvm_fault.c:627
#5  upageflttrap+0xa9 sys/arch/amd64/amd64/trap.c:192
#6  usertrap+0x430 sys/arch/amd64/amd64/trap.c:640
#7  recall_trap+0x8
Process 78613 (syz-executor) thread 0xffff800045fee018 (310499)
exclusive rwlock fdlock r = 0 (0xffff80003b7abb40)
#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  ptmioctl+0x13c sys/kern/tty_pty.c:1094
#3  VOP_IOCTL+0xac sys/kern/vfs_vops.c:264
#4  vn_ioctl+0xf8 sys/kern/vfs_vnops.c:537
#5  sys_ioctl+0x674 sys/kern/sys_generic.c:-1
#6  syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#6  syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783
#7  Xsyscall+0x128
Process 86586 (syz-executor) thread 0xffff800045fefca0 (379098)
exclusive kernel_lock &kernel_lock r = 0 (0xffffffff83acc800)
#0  witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0  witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1  __mp_acquire_count+0x58 sys/kern/kern_lock.c:-1
#2  malloc+0xe3 sys/kern/kern_malloc.c:175
#3  sys_shmat+0x9f sys/kern/sysv_shm.c:-1
#4  syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#4  syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
#5  Xsyscall+0x128
Process 15789 (systqmp) thread 0xffff800045ffe298 (249342)
shared rwlock systqmp r = 0 (0xffffffff83944c58)
#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{1}> show malloc
           Type InUse  MemUse  HighUse   Limit  Requests Type Lim
         devbuf 11056  12211K   12214K 166960K     12239        0
            pcb    20     14K      16K 166960K       107        0
         rtable   219      7K       7K 166960K       375        0
             pf    32     17K      18K 166960K        50        0
         ifaddr    39      6K       7K 166960K        47        0
        ifgroup    51      2K       2K 166960K        62        0
         sysctl     1      1K       9K 166960K         6        0
       counters    68     36K      37K 166960K        74        0
       ioctlops     0      0K       4K 166960K      1617        0
            iov     0      0K       0K 166960K         1        0
          mount     1      1K       1K 166960K         1        0
            log     0      0K       0K 166960K         4        0
         vnodes  1416     89K      89K 166960K      1511        0
      UFS quota     1     32K      32K 166960K         1        0
      UFS mount     5     36K      36K 166960K         5        0
            shm     3      5K       5K 166960K         3        0
         VM map     2      1K       1K 166960K         2        0
            sem     6      0K       0K 166960K         9        0
        dirhash    12      2K       2K 166960K        12        0
           ACPI  1692    195K     286K 166960K     12470        0
      file desc    18     65K      89K 166960K       168        0
           proc    72    115K     180K 166960K       564        0
        subproc    67      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         1        0
       in_multi    88      6K       7K 166960K        99        0
    ether_multi     1      0K       0K 166960K         1        0
            mrt     0      0K       0K 166960K         4        0
    ISOFS mount     1     32K      32K 166960K         1        0
  MSDOSFS mount     1     16K      16K 166960K         1        0
           ttys    43    201K     201K 166960K        43        0
           exec     0      0K       1K 166960K       395        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   236    161K     168K 166960K      3575        0
       UVM aobj     3      2K       2K 166960K         3        0
     pinsyscall    44     88K     103K 166960K      1358        0
        memdesc     1      4K       4K 166960K         1        0
    crypto data     1      1K       1K 166960K         1        0
            NDP    25      1K       2K 166960K        30        0
           temp    33   9114K    9121K 166960K      4197        0
         kqueue    13     20K      24K 166960K        29        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       42    0       38     1     0     1     1     0     8    0
rtentry    176      112    0       14     5     0     5     5     0     8    0
unpcb      144       54    0       37     1     0     1     1     0     8    0
syncache   336        4    0        4     1     1     0     1     0     8    0
tcpcb      736       14    0       10     1     0     1     1     0     8    0
arp        136       18    0        2     1     0     1     1     0     8    0
inpcb      328      226    0      216    12     0    12    12     0     8   10
nd6        152       23    0        3     1     0     1     1     0     8    0
kcovpl      48        8    0        1     1     0     1     1     0     8    0
ppxss      1192       1    0        1     1     0     1     1     0     8    1
pfosfp      40     1428    0     1005     5     0     5     5     0     8    0
pfosfpen   112     1428    0      714    21     0    21    21     0     8    0
pfstitem    24       17    0        0     1     0     1     1     0     8    0
pfstkey    128       17    0        0     1     0     1     1     0     8    0
pfstate    448       17    0        0     2     0     2     2     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      451    0        0    29     0    29    29     0     8    0
art_table   40      452    0        0     5     0     5     5     0     8    0
art_node    32      110    0       11     1     0     1     1     0     8    0
sysvmsgpl   40        1    0        1     1     0     1     1     0     8    1
semapl      72        5    0        1     1     0     1     1     0     8    0
shmpl      112        1    0        0     1     0     1     1     0     8    0
dirhash    1024      17    0        0     3     0     3     3     0     8    0
dino2pl    256     1623    0      155    92     0    92    92     0     8    0
ffsino     296     1623    0      155   114     0   114   114     0     8    0
nchpl      144     1863    0      159    64     0    64    64     0     8    0
vnodes     216     1854    0        0   103     0   103   103     0     8    0
namei      1024    5950    0     5950     3     1     2     2     0     8    2
percpumem   16       53    0        3     1     0     1     1     0     8    0
kstatmem   264       31    0        6     2     0     2     2     0     8    0
scsiplug    72        1    0        1     1     0     1     1     0     8    1
scxspl     216     6316    0     6316     4     3     1     3     1     8    1
plimitpl   152       33    0       16     1     0     1     1     0     8    0
sigapl     424      495    0      447     7     0     7     7     0     8    0
knotepl    120      295    0        0     9     0     9     9     0     8    0
kqueuepl   224       32    0       22     1     0     1     1     0     8    0
pipepl     344      129    0      102     3     0     3     3     0     8    0
fdescpl    528      479    0      447     3     0     3     3     0     8    0
filepl     160     2090    0     1879    18     0    18    18     0     8    8
lockfpl    104       14    0       12     1     0     1     1     0     8    0
lockfspl    48        8    0        6     1     0     1     1     0     8    0
sessionpl  144       25    0       17     1     0     1     1     0     8    0
pgrppl      48       34    0       18     1     0     1     1     0     8    0
ucredpl    104      116    0      103     1     0     1     1     0     8    0
zombiepl   144      472    0      470     2     1     1     1     0     8    0
processpl  1232     495    0      447     5     0     5     5     0     8    0
procpl     664      563    0      505     6     0     6     6     0     8    0
sockpl     752      322    0      291    18     1    17    17     0     8   13
mcl64k     65536      1    0        0     1     0     1     1     0     8    0
mcl8k      8192       4    0        0     1     0     1     1     0     8    0
mcl4k      4096     136    0        0    17     0    17    17     0     8    0
mcl2k      2048      24    0        0     3     0     3     3     0     8    0
mextrefs    64       20    0        0     1     0     1     1     0     8    0
mtagpl      96        3    0        0     1     0     1     1     0     8    0
mbufpl     256      218    0        0    14     0    14    14     0     8    0
bufpl      272     2322    0      105   148     0   148   148     0     8    0
anonpl      32     3726    0        0    31     0    31    31     0   247    0
amapchunkpl 152    9457    0     8990    21     0    21    21     0   158    1
amappl16   200     1623    0     1604     6     4     2     5     0     8    0
amappl15   192        8    0        8     1     1     0     1     0     8    0
amappl14   184      442    0      440     1     0     1     1     0     8    0
amappl13   176      128    0      114     1     0     1     1     0     8    0
amappl12   168      764    0      733     2     0     2     2     0     8    0
amappl11   160        8    0        8     1     1     0     1     0     8    0
amappl10   152       69    0       54     1     0     1     1     0     8    0
amappl9    144      278    0      278     1     1     0     1     0     8    0
amappl8    136      113    0      111     1     0     1     1     0     8    0
amappl7    128      152    0      138     1     0     1     1     0     8    0
amappl6    120      158    0      155     1     0     1     1     0     8    0
amappl5    112      103    0       93     1     0     1     1     0     8    0
amappl4    104      302    0      281     1     0     1     1     0     8    0
amappl3     96     1707    0     1596     4     0     4     4     0     8    0
amappl2     88      560    0      498     2     0     2     2     0     8    0
amappl1     80    10714    0    10084    16     1    15    15     0     8    0
amappl      88     2814    0     2656     4     0     4     4     0    92    0
uvmvnodes   80      102    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        3    0        0     1     0     1     1     0     8    0
uaddrrnd    24      479    0      447     1     0     1     1     0     8    0
uaddrbest   32        2    0        0     1     0     1     1     0     8    0
uaddr       24      479    0      447     1     0     1     1     0     8    0
vmmpekpl   168     5997    0     5956     2     0     2     2     0     8    0
vmmpepl    168    40150    0    38208    89     1    88    88     0   357    0
vmsppl     488      478    0      447     5     0     5     5     0     8    0
rwobjpl     80    14920    0    13853    25     0    25    25     0     8    1
pdppl      4096     965    0      894   103    22    81    83     0     8   10
pvpl        32     9803    0        0    81     1    80    80     0   265    0
pmappl     256      478    0      447     3     0     3     3     0     8    0
extentpl    40       45    0       27     1     0     1     1     0     8    0
phpool     112      427    0       27    12     0    12    12     0     8    0
ddb{1}> machine ddbcpu 0
Stopped at      x86_ipi_db+0x27:        addq    $0x8,%rsp
x86_ipi_db(ffffffff839c4ff0) 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
end of kernel
end trace frame: 0x7b8e089cb680, count: 12
ddb{0}> trace
x86_ipi_db(ffffffff839c4ff0) 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
end of kernel
end trace frame: 0x7b8e089cb680, count: -3
ddb{0}> machine ddbcpu 1
Stopped at      sys_shmat+0x453:        movq    0(%r15),%rdi
sys_shmat(ffff800045fefca0,ffff80003a3a3b70,ffff80003a3a3ac0) at sys_shmat+0x453 sys/kern/sysv_shm.c:290
syscall(ffff80003a3a3b70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003a3a3b70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f1222a96e0, count: 12
ddb{1}> trace
sys_shmat(ffff800045fefca0,ffff80003a3a3b70,ffff80003a3a3ac0) at sys_shmat+0x453 sys/kern/sysv_shm.c:290
syscall(ffff80003a3a3b70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003a3a3b70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x7f1222a96e0, count: -3

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/07 03:50 openbsd 228829a254a6 fcece630 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
2026/07/02 10:04 openbsd 30d0e3967450 27192279 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
2026/07/02 05:21 openbsd 30d0e3967450 27192279 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
2026/06/25 15:12 openbsd 452256cb16b9 432fd51a .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
2026/06/24 23:00 openbsd 7c9581f1cd1a cfa969bf .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
* Struck through repros no longer work on HEAD.