syzbot


uvm_fault: ffs_nodealloccg (4)

Status: upstream: reported on 2026/03/29 00:14
Reported-by: syzbot+18c0da8db2b18571ff77@syzkaller.appspotmail.com
First crash: 67d, last: 10d
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
openbsd uvm_fault: ffs_nodealloccg -1 1 1592d 1592d 0/3 auto-closed as invalid on 2022/04/24 17:10
openbsd uvm_fault: ffs_nodealloccg (2) -1 2 628d 629d 0/3 auto-obsoleted due to no activity on 2024/12/13 04:19
openbsd uvm_fault: ffs_nodealloccg (3) -1 1 251d 251d 0/3 auto-obsoleted due to no activity on 2025/12/25 04:08

Sample crash report:
uvm_fault(0xffffffff83aba540, 0xffff80001a612004, 0, 1) -> d
kernel: page fault trap, code=0
Stopped at      ffs_nodealloccg+0x13c:  movl    0x4(%rbx),%r15d
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*483506  44752      0         0x2          0    0K syz-executor
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c ffs_cgread sys/ufs/ffs/ffs_alloc.c:856 [inline]
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c sys/ufs/ffs/ffs_alloc.c:1106
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a ffs_hashalloc sys/ufs/ffs/ffs_alloc.c:814 [inline]
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a sys/ufs/ffs/ffs_alloc.c:390
ufs_mkdir(ffff80002a362780) at ufs_mkdir+0xfc sys/ufs/ufs/ufs_vnops.c:1112
VOP_MKDIR(fffffd806f6976f0,ffff80002a3628e0,ffff80002a362910,ffff80002a362810) at VOP_MKDIR+0x101 sys/kern/vfs_vops.c:394
domkdirat(ffff80002a2234d0,ffffff9c,75ea85013c00,1c0) at domkdirat+0x179 sys/kern/vfs_syscalls.c:3149
syscall(ffff80002a362a90) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80002a362a90) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x75ea85013bc0, 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{0}> 
ddb{0}> set $lines = 0
ddb{0}> set $maxwidth = 0
ddb{0}> show panic
*cpu0: uvm_fault(0xffffffff83aba540, 0xffff80001a612004, 0, 1) -> d
ddb{0}> trace
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c ffs_cgread sys/ufs/ffs/ffs_alloc.c:856 [inline]
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c sys/ufs/ffs/ffs_alloc.c:1106
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a ffs_hashalloc sys/ufs/ffs/ffs_alloc.c:814 [inline]
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a sys/ufs/ffs/ffs_alloc.c:390
ufs_mkdir(ffff80002a362780) at ufs_mkdir+0xfc sys/ufs/ufs/ufs_vnops.c:1112
VOP_MKDIR(fffffd806f6976f0,ffff80002a3628e0,ffff80002a362910,ffff80002a362810) at VOP_MKDIR+0x101 sys/kern/vfs_vops.c:394
domkdirat(ffff80002a2234d0,ffffff9c,75ea85013c00,1c0) at domkdirat+0x179 sys/kern/vfs_syscalls.c:3149
syscall(ffff80002a362a90) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80002a362a90) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x75ea85013bc0, count: -7
ddb{0}> show registers
rdi                                0
rsi                                0
rbp               0xffff80002a362530
rbx               0xffff80001a612000
rdx                                0
rcx               0xffff80002a2234d0
rax               0xffffffff83913ff0    cpu_info_full_primary+0x1ff0
r8                0xffffffffffffffff
r9                0xfffffd80097fd6e8
r10               0x8b77dc808712a0cc
r11               0xbee39bebb88f143b
r12               0xffff800000c31800
r13               0xfffffd8071c78030
r14                                0
r15                                0
rip               0xffffffff833be21c    ffs_nodealloccg+0x13c
cs                               0x8
rflags                       0x10246    __ALIGN_SIZE+0xf246
rsp               0xffff80002a362480
ss                              0x10
ffs_nodealloccg+0x13c:  movl    0x4(%rbx),%r15d
ddb{0}> show proc
PROC (syz-executor) tid=483506 pid=44752 tcnt=1 stat=onproc
    flags process=2<EXEC> proc=0
    runpri=36, usrpri=50, slppri=36, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff80002a2227d8,0xffffffff839e2ce0
    process=0xffff80002a383038 user=0xffff80002a35d000, vmspace=0xfffffd800b0633d0
    estcpu=36, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{0}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
*44752  483506  34911      0  7         0x2                syz-executor
 65768  208542      1      0  3    0x100083  ttyin         getty
 34911  224051      1      0  3        0x82  nanoslp       syz-executor
 44656   60642      0      0  3     0x14200  bored         smr
  8838  465663      0      0  3     0x14200  pgzero        zerothread
 76626  249820      0      0  3     0x14200  aiodoned      aiodoned
 84289   21306      0      0  3     0x14200  syncer        update
 47400  116101      0      0  3     0x14200  cleaner       cleaner
 41759  398093      0      0  3     0x14200  reaper        reaper
 71546  139777      0      0  3     0x14200  pgdaemon      pagedaemon
 44690  460412      0      0  3     0x14200  bored         viomb
 77306  392836      0      0  3  0x40014200  acpi0         acpi0
 21678  440628      0      0  7  0x40014200                idle1
  2907  454398      0      0  3     0x14200  bored         softnet1
 76662  243710      0      0  3     0x14200  bored         softnet0
  6192  417042      0      0  3     0x14200  smrbar        systqmp
 57706  296575      0      0  3     0x14200  bored         systq
  6620  222059      0      0  3     0x14200  tmoslp        softclockmp
  7367  324331      0      0  3  0x40014200  tmoslp        softclock
 74056  148581      0      0  3  0x40014200                idle0
     1  234102      0      0  3        0x82  wait          init
     0       0     -1      0  3     0x10200  scheduler     swapper
ddb{0}> show all locks
Process 44752 (syz-executor) thread 0xffff80002a2234d0 (483506)
Process 6192 (systqmp) thread 0xffff8000ffffea60 (417042)
ddb{0}> show malloc
           Type InUse  MemUse  HighUse   Limit  Requests Type Lim
         devbuf 11027  12001K   14108K 166960K     13406        0
            pcb    17     16K      18K 166960K       180        0
         rtable    63      4K       9K 166960K       998        0
             pf    22     16K      25K 166960K       161        0
         ifaddr    13      2K       8K 166960K       141        0
        ifgroup    22      1K       2K 166960K       159        0
         sysctl     4      1K       9K 166960K        10        0
       counters    54     35K      37K 166960K       148        0
       ioctlops     0      0K       4K 166960K      1736        0
            iov     0      0K      16K 166960K        53        0
          mount     1      1K       1K 166960K         1        0
            log     0      0K       0K 166960K         4        0
         vnodes  1481     93K      94K 166960K      2121        0
      UFS quota     1     32K      32K 166960K         1        0
      UFS mount     5     36K      36K 166960K         5        0
            shm     2      1K       5K 166960K         7        0
         VM map     2      1K       1K 166960K         2        0
            sem    12      0K       0K 166960K        61        0
        dirhash    12      2K       2K 166960K        12        0
           ACPI  1692    195K     286K 166960K     12470        0
      file desc     2      2K      93K 166960K       864        0
          sigio     0      0K       0K 166960K         3        0
           proc    21     33K     196K 166960K      1128        0
        subproc     0      0K       4K 166960K       243        0
    NFS srvsock     1      0K       0K 166960K         1        0
     NFS daemon     1     16K      16K 166960K         1        0
    ip_moptions     0      0K       0K 166960K        73        0
       in_multi    17      1K       7K 166960K       344        0
    ether_multi     1      0K       0K 166960K         3        0
            mrt     0      0K       0K 166960K        22        0
    ISOFS mount     1     32K      32K 166960K         1        0
  MSDOSFS mount     1     16K      16K 166960K         1        0
           ttys    67    307K     307K 166960K        67        0
           exec     0      0K       1K 166960K       716        0
   fusefs mount     1     32K      32K 166960K         1        0
     pfkey data     0      0K       0K 166960K         1        0
            tdb     3      0K       0K 166960K         3        0
        VM swap     8     62K      64K 166960K        10        0
       UVM amap    22      6K     168K 166960K      8444        0
       UVM aobj    74      3K       3K 166960K        76        0
     pinsyscall     5     10K     105K 166960K      2618        0
        memdesc     1      4K       4K 166960K         1        0
    crypto data     1      1K       1K 166960K         1        0
    ip6_options     0      0K       0K 166960K        82        0
            NDP     4      0K       2K 166960K        95        0
           temp    42   9122K    9191K 166960K     17685        0
         kqueue     1      2K      32K 166960K       121        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       91    0       91     1     0     1     1     0     8    1
rtentry    176      334    0      320     6     0     6     6     0     8    3
unpcb      144      273    0      273     3     2     1     3     0     8    1
syncache   336        6    0        6     1     1     0     1     0     8    0
tcpcb      736       98    0       97     1     0     1     1     0     8    0
arp        136       59    0       56     1     0     1     1     0     8    0
inpcb      328      673    0      672     7     5     2     7     0     8    1
nd6        152       82    0       82     1     0     1     1     0     8    1
pkpcb       40        3    0        3     2     2     0     1     0     8    0
kcovpl      48       27    0       27     1     0     1     1     0     8    1
ppxss      1192      18    0       18     2     1     1     1     0     8    1
pppxif     1576       1    0        1     1     1     0     1     0     8    0
pfstscr     40        7    0        5     1     0     1     1     0     8    0
pffrag     232        4    0        1     1     0     1     1     0   482    0
pffrnode    88        4    0        1     1     0     1     1     0     8    0
pffrent     40        5    0        2     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
pfsrclim   320        3    0        3     1     1     0     1     0     8    0
pfanchor   1288       8    0        0     1     0     1     1     0     8    0
pftag       88        1    0        0     1     0     1     1     0     8    0
pfqueue    320        1    0        1     1     1     0     1     0     8    0
pfstitem    24       44    0       15     1     0     1     1     0     8    0
pfstkey    128       49    0       20     2     0     2     2     0     8    0
pfstate    448       47    0       19     5     0     5     5     0     8    0
pfrule     1360      26    0       20     2     1     1     2     0     8    0
art_heap8  4096       3    0        0     3     0     3     3     0     8    0
art_heap4  256     1434    0     1300    31     7    24    31     0     8    7
art_table   40     1437    0     1300     6     0     6     6     0     8    1
art_node    32      334    0      313     1     0     1     1     0     8    0
sysvmsgpl   40        4    0        2     1     0     1     1     0     8    0
semapl      72       59    0       49     1     0     1     1     0     8    0
shmpl      112       73    0        2     3     0     3     3     0     8    0
dirhash    1024      17    0        0     3     0     3     3     0     8    0
dino2pl    256     2328    0      820    95     0    95    95     0     8    0
ffsino     296     2378    0      870   117     0   117   117     0     8    0
nchpl      144     3040    0     1268    66     0    66    66     0     8    0
rtmask      32        6    0        6     1     1     0     1     0     8    0
vnodes     216     3051    0        0   170     0   170   170     0     8    0
namei      1024   11623    0    11622     2     0     2     2     0     8    1
percpumem   16       89    0       47     1     0     1     1     0     8    0
kstatmem   264       85    0       74     2     0     2     2     0     8    1
scsiplug    72        5    0        5     2     1     1     1     0     8    1
scxspl     216    28462    0    28462    10     9     1     8     1     8    1
plimitpl   152      131    0      122     1     0     1     1     0     8    0
sigapl     424     1139    0     1112     7     1     6     7     0     8    2
knotepl    120      530    0        0    17     0    17    17     0     8    0
kqueuepl   224      208    0      207     5     2     3     3     0     8    2
pipepl     344      388    0      361     7     3     4     6     0     8    1
fdescpl    528     1123    0     1118     3     0     3     3     0     8    0
filepl     160     5454    0     5404    15     4    11    15     0     8    5
lockfpl    104      157    0      157     1     0     1     1     0     8    1
lockfspl    48       70    0       70     1     0     1     1     0     8    1
sessionpl  144      122    0      119     1     0     1     1     0     8    0
pgrppl      48      202    0      192     1     0     1     1     0     8    0
ucredpl    104      573    0      569     1     0     1     1     0     8    0
zombiepl   144     1118    0     1112     1     0     1     1     0     8    0
processpl  1232    1139    0     1112     5     1     4     5     0     8    0
procpl     664     1753    0     1726     6     1     5     6     0     8    2
sosppl     176        1    0        1     1     1     0     1     0     8    0
sockpl     752     1050    0     1049    11     7     4    11     0     8    3
mcl64k     65536      8    0        0     1     0     1     1     0     8    0
mcl12k     12288      1    0        0     1     0     1     1     0     8    0
mcl8k      8192       2    0        0     1     0     1     1     0     8    0
mcl4k      4096     129    0        0    17     1    16    17     0     8    0
mcl2k      2048      27    0        0     4     0     4     4     0     8    0
mtagpl      96        6    0        0     1     0     1     1     0     8    0
mbufpl     256      315    0        0    20     0    20    20     0     8    0
bufpl      280    13471    0     7207   448     0   448   448     0     8    0
anonpl      32     8574    0        0    70     0    70    70     0   246    0
amapchunkpl 152   25268    0    25215    27     9    18    27     0   158   11
amappl16   200     2548    0     2548    17    12     5    15     0     8    5
amappl15   192        9    0        9     1     1     0     1     0     8    0
amappl14   184      661    0      661     1     0     1     1     0     8    1
amappl13   176      176    0      175     1     0     1     1     0     8    0
amappl12   168     1502    0     1499     2     0     2     2     0     8    0
amappl11   160        6    0        5     2     1     1     1     0     8    0
amappl10   152       69    0       69     1     0     1     1     0     8    1
amappl9    144      276    0      276     1     1     0     1     0     8    0
amappl8    136      176    0      175     1     0     1     1     0     8    0
amappl7    128      185    0      183     1     0     1     1     0     8    0
amappl6    120      349    0      349     1     0     1     1     0     8    1
amappl5    112       95    0       94     1     0     1     1     0     8    0
amappl4    104      386    0      383     1     0     1     1     0     8    0
amappl3     96     5082    0     5071     4     0     4     4     0     8    1
amappl2     88      703    0      694     2     0     2     2     0     8    0
amappl1     80    14844    0    14799    15     3    12    15     0     8    8
amappl      88     7222    0     7205     5     1     4     5     0    92    0
uvmvnodes   80      116    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      254    0      254     2     1     1     1     0     8    1
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       19    0       18     1     0     1     1     0     8    0
aobjpl      72       75    0        2     2     0     2     2     0     8    0
uaddrrnd    24     1124    0     1119     1     0     1     1     0     8    0
uaddrbest   32        2    0        0     1     0     1     1     0     8    0
uaddr       24     1124    0     1119     1     0     1     1     0     8    0
vmmpekpl   168    11028    0    11005     3     0     3     3     0     8    0
vmmpepl    168    79959    0    79794    98    10    88    98     0   357   52
vmsppl     488     1123    0     1119     5     1     4     5     0     8    2
rwobjpl     80    24083    0    23802    29     1    28    29     0     8    2
pdppl      4096    2255    0     2238   115    82    33    83     0     8   16
pvpl        32    14537    0        0   119     1   118   119     0   265    0
pmappl     256     1123    0     1119     3     0     3     3     0     8    0
extentpl    40       45    0       27     1     0     1     1     0     8    0
phpool     112      307    0       94     8     0     8     8     0     8    0
ddb{0}> machine ddbcpu 0
Invalid cpu 0
ddb{0}> trace
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c ffs_cgread sys/ufs/ffs/ffs_alloc.c:856 [inline]
ffs_nodealloccg(fffffd806f674aa0,0,0,41c0) at ffs_nodealloccg+0x13c sys/ufs/ffs/ffs_alloc.c:1106
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a ffs_hashalloc sys/ufs/ffs/ffs_alloc.c:814 [inline]
ffs_inode_alloc(fffffd806f674aa0,41c0,fffffd80097fd6e8,ffff80002a362718) at ffs_inode_alloc+0x20a sys/ufs/ffs/ffs_alloc.c:390
ufs_mkdir(ffff80002a362780) at ufs_mkdir+0xfc sys/ufs/ufs/ufs_vnops.c:1112
VOP_MKDIR(fffffd806f6976f0,ffff80002a3628e0,ffff80002a362910,ffff80002a362810) at VOP_MKDIR+0x101 sys/kern/vfs_vops.c:394
domkdirat(ffff80002a2234d0,ffffff9c,75ea85013c00,1c0) at domkdirat+0x179 sys/kern/vfs_syscalls.c:3149
syscall(ffff80002a362a90) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff80002a362a90) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x75ea85013bc0, count: -7
ddb{0}> machine ddbcpu 1
Stopped at      x86_ipi_db+0x27:        addq    $0x8,%rsp
x86_ipi_db(ffff80002999dff0) 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(ffff80002999dff0) at sched_idle+0x371 sys/kern/kern_sched.c:192
end trace frame: 0x0, count: 10
ddb{1}> trace
x86_ipi_db(ffff80002999dff0) 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(ffff80002999dff0) at sched_idle+0x371 sys/kern/kern_sched.c:192
end trace frame: 0x0, count: -5
ddb{1}> 

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/25 13:02 openbsd 3ca1fbf96c86 c69befb3 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: ffs_nodealloccg
2026/05/06 01:42 openbsd eec9cf095b26 340bcdf0 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-main uvm_fault: ffs_nodealloccg
2026/05/01 21:27 openbsd bedf3632bee6 340bcdf0 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: ffs_nodealloccg
2026/04/02 13:15 openbsd 8eafb9a57fa3 4b3d9a38 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: ffs_nodealloccg
2026/03/29 18:42 openbsd 8c0bc7d7b019 4b3d9a38 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: ffs_nodealloccg
2026/03/29 00:13 openbsd b39c1312a589 4b3d9a38 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore uvm_fault: ffs_nodealloccg
* Struck through repros no longer work on HEAD.