syzbot


uvm_fault: sys_shmat (2)

Status: upstream: reported on 2025/10/01 08:49
Reported-by: syzbot+9669e87e543ae1f05884@syzkaller.appspotmail.com
First crash: 61d, last: 9h04m
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
openbsd uvm_fault: sys_shmat -1 1 156d 156d 0/3 auto-obsoleted due to no activity on 2025/09/26 10:39

Sample crash report:
uvm_fault(0xffffffff838cddc0, 0xffff800001566000, 0, 2) -> e
kernel: page fault trap, code=2
Stopped at      sys_shmat+0xe0: movl    $0xffffffffffffffff,0(%r14)
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*147873  19292      0           0  0x4000000    0K syz-executor
sys_shmat(ffff8000ffff2548,ffff80003c44fc00,ffff80003c44fb50) at sys_shmat+0xe0 sys/kern/sysv_shm.c:235
syscall(ffff80003c44fc00) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c44fc00) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xab573a7a820, 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{0}> 
ddb{0}> set $lines = 0
ddb{0}> set $maxwidth = 0
ddb{0}> show panic
*cpu0: uvm_fault(0xffffffff838cddc0, 0xffff800001566000, 0, 2) -> e
ddb{0}> trace
sys_shmat(ffff8000ffff2548,ffff80003c44fc00,ffff80003c44fb50) at sys_shmat+0xe0 sys/kern/sysv_shm.c:235
syscall(ffff80003c44fc00) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c44fc00) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xab573a7a820, count: -3
ddb{0}> show registers
rdi               0xffff8000333e6000
rsi                           0xdf78    __ALIGN_SIZE+0xcf78
rbp               0xffff80003c44fb20
rbx               0xffff80003c44fc00
rdx               0xffff8000333e6000
rcx                           0xdf77    __ALIGN_SIZE+0xcf77
rax               0xffffffff82c7c082    sys_shmat+0xf2
r8                0xffffffffffffffff
r9                                 0
r10               0xfb7c6a286084d61a
r11               0x2e835a1769e85140
r12               0xffff8000ffff2548
r13               0xffff800001488000
r14               0xffff800001566000
r15                           0xde00    __ALIGN_SIZE+0xce00
rip               0xffffffff82c7c070    sys_shmat+0xe0
cs                               0x8
rflags                       0x10216    __ALIGN_SIZE+0xf216
rsp               0xffff80003c44fa90
ss                              0x10
sys_shmat+0xe0: movl    $0xffffffffffffffff,0(%r14)
ddb{0}> show proc
PROC (syz-executor) tid=147873 pid=19292 tcnt=4 stat=onproc
    flags process=0 proc=4000000<THREAD>
    runpri=85, usrpri=85, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff8000ffff3770,0xffff8000ffff22c0
    process=0xffff80003c41c030 user=0xffff80003c44a000, vmspace=0xfffffd806e2e2400
    estcpu=35, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{0}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
 90898  147060  17048      0  2           0                syz-executor
 90898  328691  17048      0  3   0x4000080  fsleep        syz-executor
 20474  143222  86082      0  2           0                syz-executor
 20474   46327  86082      0  2   0x4000000                syz-executor
 32781  421176  59298      0  2           0                syz-executor
 19292  291836   5140      0  2           0                syz-executor
 19292  170383   5140      0  2   0x4000000                syz-executor
*19292  147873   5140      0  7   0x4000000                syz-executor
 19292  359187   5140      0  3   0x4000080  fsleep        syz-executor
 43629   23378  98248      0  2           0                syz-executor
 43629  442430  98248      0  3   0x4000080  fsleep        syz-executor
 43629  281242  98248      0  3   0x4000080  fsleep        syz-executor
 43629   24225  98248      0  3   0x4000080  fsleep        syz-executor
  5245  303255  71558      0  2           0                syz-executor
  5245   99604  71558      0  2   0x4000000                syz-executor
  5245   38966  71558      0  2   0x4000000                syz-executor
 90759  404834      1      0  3    0x100083  ttyin         getty
 71558  505671  30179      0  3        0x82  nanoslp       syz-executor
  5140    2619  30179      0  2         0x3                syz-executor
 98248  446744  30179      0  2         0x3                syz-executor
 59298  394153  30179      0  3        0x82  nanoslp       syz-executor
 88142  348515  30179      0  2         0x2                syz-executor
 86082  330646  30179      0  3        0x82  nanoslp       syz-executor
 17048  404824  30179      0  3        0x82  nanoslp       syz-executor
 32132  317407  30179      0  2         0x3                syz-executor
 30179  296533  67687      0  3        0x82  kqread        syz-executor
 67687  205176  54967      0  3    0x10008a  sigsusp       ksh
 54967  123657  76162      0  3        0x98  kqread        sshd-session
 76162  397226  96306      0  3        0x92  kqread        sshd-session
 96306  456110      1      0  3        0x88  kqread        sshd
 11660  266175  77885     74  3   0x1100092  bpf           pflogd
 77885  414954      1      0  3        0x80  sbwait        pflogd
 91627  271169  72914     73  3   0x1100090  kqread        syslogd
 72914  185190      1      0  3    0x100082  sbwait        syslogd
 15332  197552      1      0  3    0x100080  kqread        resolvd
 49583  155836  79123     77  3    0x100092  kqread        dhcpleased
 61144   69326  79123     77  3    0x100092  kqread        dhcpleased
 79123  319310      1      0  3        0x80  kqread        dhcpleased
 38835  312960      0      0  3     0x14200  bored         smr
 20941  331540      0      0  2     0x14200                zerothread
 81624  399952      0      0  3     0x14200  aiodoned      aiodoned
 84600  169501      0      0  3     0x14200  syncer        update
  4587  400150      0      0  3     0x14200  cleaner       cleaner
 79096  405263      0      0  3     0x14200  reaper        reaper
  1669  152532      0      0  3     0x14200  pgdaemon      pagedaemon
 93135  469543      0      0  3     0x14200  bored         viomb
 71608    2800      0      0  3  0x40014200  acpi0         acpi0
 22837  454049      0      0  7  0x40014200                idle1
 51921  472785      0      0  3     0x14200  bored         softnet1
 57073  398619      0      0  3     0x14200  bored         softnet0
 73897  517050      0      0  3     0x14200  bored         systqmp
 16348  330334      0      0  3     0x14200  bored         systq
 14640   86807      0      0  3     0x14200  tmoslp        softclockmp
 33917  310292      0      0  3  0x40014200  tmoslp        softclock
 28186  436688      0      0  3  0x40014200                idle0
     1  230038      0      0  3        0x82  wait          init
     0       0     -1      0  3  0x10010200  scheduler     swapper
ddb{0}> show all locks
Process 20474 (syz-executor) thread 0xffff80003c00d248 (46327)
Process 19292 (syz-executor) thread 0xffff8000ffff2548 (147873)
Process 5245 (syz-executor) thread 0xffff8000ffffc538 (99604)
Process 88142 (syz-executor) thread 0xffff8000ffffd760 (348515)
ddb{0}> show malloc
           Type InUse  MemUse  HighUse   Limit  Requests Type Lim
         devbuf 10234  11037K   11369K 166960K     13276        0
            pcb    17     15K      17K 166960K       491        0
         rtable   266     13K      13K 166960K       559        0
             pf    40     19K      81K 166960K       156        0
         ifaddr    44      8K       8K 166960K        96        0
        ifgroup    55      2K       2K 166960K       159        0
         sysctl     3      1K       9K 166960K        16        0
       counters    70     37K      38K 166960K       318        0
       ioctlops     0      0K       4K 166960K      1838        0
            iov     0      0K      20K 166960K       112        0
          mount     1      1K       1K 166960K         1        0
            log     0      0K       0K 166960K         4        0
         vnodes  1400     88K      89K 166960K      2518        0
      UFS quota     1     32K      32K 166960K         1        0
      UFS mount     5     36K      36K 166960K         5        0
            shm     3      6K       6K 166960K        21        0
         VM map     2      1K       1K 166960K         2        0
            sem    12      0K       1K 166960K        46        0
        dirhash    51      9K      11K 166960K       246        0
           ACPI  1692    195K     286K 166960K     12470        0
      file desc    18     65K     102K 166960K      1283        0
          sigio     0      0K       0K 166960K        33        0
           proc    74    115K     164K 166960K       717        0
        subproc    72      4K       4K 166960K        81        0
    NFS srvsock     1      0K       0K 166960K         1        0
     NFS daemon     1     16K      16K 166960K         1        0
    ip_moptions     0      0K       0K 166960K       210        0
       in_multi    99      7K       7K 166960K       159        0
    ether_multi     1      0K       0K 166960K        10        0
            mrt     2      0K       0K 166960K        12        0
    ISOFS mount     1     32K      32K 166960K         1        0
  MSDOSFS mount     1     16K      16K 166960K         1        0
           ttys   265   1182K    1182K 166960K       265        0
           exec     0      0K       1K 166960K       749        0
   fusefs mount     1     32K      32K 166960K         1        0
     pfkey data     0      0K       0K 166960K         4        0
            tdb     3      0K       0K 166960K         3        0
        VM swap     8     62K      64K 166960K        10        0
       UVM amap   245    151K     166K 166960K     14316        0
       UVM aobj    33     14K      14K 166960K        39        0
     pinsyscall    43     86K     101K 166960K      2477        0
        memdesc     1      4K       4K 166960K         1        0
    crypto data     1      1K       1K 166960K         1        0
    ip6_options     0      0K       0K 166960K       113        0
            NDP    12      0K       2K 166960K        68        0
           temp    68   8677K    8752K 166960K     65559        0
         kqueue    13     20K      31K 166960K       231        0
      SYN cache     2     16K      16K 166960K         2        0
ddb{0}> show all pools
Name      Size Requests Fail Releases Pgreq Pgrel Npage Hiwat Minpg Maxpg Idle
plcache    128       26    0        0     1     0     1     1     0     8    0
rtpcb      120      257    0      254     5     4     1     5     0     8    0
rtentry    176      161    0       52     6     0     6     6     0     8    0
unpcb      144     1029    0     1011    15    14     1     6     0     8    0
syncache   336        6    0        6     4     3     1     1     0     8    1
tcpqe       32        3    0        3     2     1     1     1     0     8    1
tcpcb      736      310    0      304     3     2     1     2     0     8    0
arp        136       28    0        7     1     0     1     1     0     8    0
ipq         40        3    0        3     3     2     1     1     0     8    1
ipqe        40        9    0        9     3     2     1     1     0     8    1
inpcb      328     1732    0     1721    35    31     4    15     0     8    2
nd6        152       30    0        3     2     0     2     2     0     8    0
pkpcb       40        9    0        9     5     5     0     1     0     8    0
kcovpl      48        9    0        1     1     0     1     1     0     8    0
ppxss      1192     115    0      115     3     2     1     1     0     8    1
pppxif     1504       3    0        3     1     1     0     1     0     8    0
pfstscr     40        3    0        2     1     0     1     1     0     8    0
pffrag     232       12    0        5     1     0     1     1     0   482    0
pffrnode    88       11    0        5     1     0     1     1     0     8    0
pffrent     40       33    0       26     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       3    0        2     2     1     1     1     0     8    0
pfanchor   1288       2    0        0     1     0     1     1     0     8    0
pfanchor: pool(0xffffffff838ea818:pfanchor): page inconsistency: page 0xffff8000ffffffff; at page head addr 0xffff80000150bf90 (p 0xffff800001508000)
uvm_fault(0xfffffd806e2e2400, 0x10000004f, 0, 1) -> e
kernel: page fault trap, code=0
Faulted in DDB; continuing...
ddb{0}> machine ddbcpu 0
Invalid cpu 0
ddb{0}> trace
sys_shmat(ffff8000ffff2548,ffff80003c44fc00,ffff80003c44fb50) at sys_shmat+0xe0 sys/kern/sysv_shm.c:235
syscall(ffff80003c44fc00) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80003c44fc00) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:775
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xab573a7a820, count: -3
ddb{0}> machine ddbcpu 1
Stopped at      x86_ipi_db+0x27:        addq    $0x8,%rsp
x86_ipi_db(ffff8000299edff0) 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
acpicpu_idle() at acpicpu_idle+0x457 sys/dev/acpi/acpicpu_x86.c:1224
sched_idle(ffff8000299edff0) at sched_idle+0x391 sys/kern/kern_sched.c:191
end trace frame: 0x0, count: 10
ddb{1}> trace
x86_ipi_db(ffff8000299edff0) 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
acpicpu_idle() at acpicpu_idle+0x457 sys/dev/acpi/acpicpu_x86.c:1224
sched_idle(ffff8000299edff0) at sched_idle+0x391 sys/kern/kern_sched.c:191
end trace frame: 0x0, count: -5

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/01 22:42 openbsd 6cbdb9457802 d4611817 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: sys_shmat
2025/11/18 14:29 openbsd ae8b598acb72 ef766cd7 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-main uvm_fault: sys_shmat
2025/10/01 08:49 openbsd ae814b404f5c 770ff59f .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.