syzbot


witness: reversal: sbufsnd inode (4)

Status: upstream: reported on 2026/05/23 21:30
Reported-by: syzbot+de15d066c25df21a5697@syzkaller.appspotmail.com
First crash: 3d08h, last: 3d08h
Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
openbsd witness: reversal: sbufsnd inode (3) -1 39 125d 350d 0/3 auto-obsoleted due to no activity on 2026/04/14 02:39
openbsd witness: reversal: sbufsnd inode (2) -1 19 413d 464d 0/3 auto-obsoleted due to no activity on 2025/05/28 20:57
openbsd witness: reversal: sbufsnd inode -1 4 583d 649d 0/3 auto-obsoleted due to no activity on 2025/01/18 21:43

Sample crash report:
pf: key search, in on vio0: TCPwitness:  wire: (0) lock order reversal:
10.128.15.235 1st 0xffff800010fdf388 sbufsnd (&so->so_snd.sb_lock)
:30002 2nd 0xfffffd80757b3a50 inode (&ip->i_lock)
 10.128.0.133lock order [1] sbufsnd (&so->so_snd.sb_lock) -> [2] inode (&ip->i_lock)
:8698lock order data 0xffffffff8351aafa -> 0xffffffff8348b191 is missing

lock order [2] inode (&ip->i_lock) -> [3] sbufrcv (&so->so_rcv.sb_lock)
pf: key search, in on vio0: #0  TCP wire: (0) 10.128.15.235:30002 10.128.0.133:8698
pf: key search, out on vio0: TCP wire: (0) 10.128.15.235:30002 10.128.0.133:8698
rw_do_enter_write+0xba
#1  sblock+0xb6 sys/kern/uipc_socket2.c:536
#2  soreceive+0x27d sys/kern/uipc_socket.c:890
#3  fifo_read+0x117 sys/miscfs/fifofs/fifo_vnops.c:264
#4  VOP_READ+0x101 sys/kern/vfs_vops.c:227
#5  vn_rdwr+0x15b sys/kern/vfs_vnops.c:-1
#6  vndsetcred+0xa1 sys/dev/vnd.c:685
#7  vndioctl+0xdfc sys/dev/vnd.c:486
#8  VOP_IOCTL+0xac sys/kern/vfs_vops.c:264
#9  vn_ioctl+0xf8 sys/kern/vfs_vnops.c:537
#10 sys_ioctl+0x674 sys/kern/sys_generic.c:-1
#11 syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#11 syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783
#12 Xsyscall+0x128
lock order [3] sbufrcv (&so->so_rcv.sb_lock) -> [1] sbufsnd (&so->so_snd.sb_lock)
#0  rw_do_enter_write+0xba sys/kern/kern_rwlock.c:234
#1  sblock+0xb6 sys/kern/uipc_socket2.c:536
#2  sosplice+0x312 sys/kern/uipc_socket.c:1347
#3  sys_setsockopt+0x2ba sys/kern/uipc_syscalls.c:1226
#4  syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#4  syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783
#5  Xsyscall+0x128
Stopped at      db_enter+0x25:  addq    $0x8,%rsp
ddb{0}> 
ddb{0}> set $lines = 0
ddb{0}> set $maxwidth = 0
ddb{0}> show panic
the kernel did not panic
ddb{0}> trace
db_enter() at db_enter+0x25 sys/arch/amd64/amd64/db_interface.c:438
witness_checkorder(fffffd80757b3a50,9,0) at witness_checkorder+0x10d1 sys/kern/subr_witness.c:-1
rw_do_enter_write(fffffd80757b3a38,1) at rw_do_enter_write+0xba sys/kern/kern_rwlock.c:234
rrw_enter(fffffd80757b3a38,1) at rrw_enter+0xc6 sys/kern/kern_rwlock.c:621
VOP_LOCK(fffffd806ebf9bd0,2001) at VOP_LOCK+0xbd sys/kern/vfs_vops.c:527
vn_lock(fffffd806ebf9bd0,2001) at vn_lock+0xa4 sys/kern/vfs_vnops.c:576
vfs_lookup(ffff800030f8b330) at vfs_lookup+0x12b sys/kern/vfs_lookup.c:431
namei(ffff800030f8b330) at namei+0x7c5 sys/kern/vfs_lookup.c:250
unp_connect(ffff800010fdf1a0,fffffd806a767900,ffff8000fffef770) at unp_connect+0x29d sys/kern/uipc_usrreq.c:872
uipc_dgram_send(ffff800010fdf1a0,fffffd806c581800,fffffd806a767900,0) at uipc_dgram_send+0x163 sys/kern/uipc_usrreq.c:609
sosend(ffff800010fdf1a0,fffffd806a767900,ffff800030f8b5b8,0,0,0) at sosend+0x804 sys/kern/uipc_socket.c:-1
sendit(ffff8000fffef770,3,ffff800030f8b738,0,ffff800030f8b7f0) at sendit+0x5a5 sys/kern/uipc_syscalls.c:785
sys_sendmsg(ffff8000fffef770,ffff800030f8b8a0,ffff800030f8b7f0) at sys_sendmsg+0x246 sys/kern/uipc_syscalls.c:603
syscall(ffff800030f8b8a0) at syscall+0xbd4 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff800030f8b8a0) at syscall+0xbd4 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xbb82d6d62f0, count: -15
ddb{0}> show registers
rdi                                0
rsi                          0x80000    acpi_pdirpa+0x6be71
rbp               0xffff800030f8afa0
rbx                                0
rdx               0xffff8000015d1e40
rcx               0xffff8000fffef770
rax                          0x7ffff    acpi_pdirpa+0x6be70
r8                0xffff800030f8ae80
r9                0x8080808080808080
r10                0x765d39894906a44
r11               0x9597640393e55757
r12               0xfffffd80040bd8c0
r13               0xfffffd80048a5f00
r14                              0x3
r15               0xffffffff835277b3    substchar+0xbde8
rip               0xffffffff82e5bf15    db_enter+0x25
cs                               0x8
rflags                         0x246
rsp               0xffff800030f8af90
ss                              0x10
db_enter+0x25:  addq    $0x8,%rsp
ddb{0}> show proc
PROC (syz-executor) tid=257671 pid=5839 tcnt=2 stat=onproc
    flags process=10<SUGID> proc=4000000<THREAD>
    runpri=32, usrpri=50, slppri=32, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff8000fffee7e0,0xffffffff83af0ad0
    process=0xffff80002a37d358 user=0xffff800030f86000, vmspace=0xfffffd806f33d1f0
    estcpu=36, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{0}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
  5839  508903  31887  60929  2        0x10                syz-executor
* 5839  257671  31887  60929  7   0x4000010                syz-executor
 11370  379394  79994      0  2           0                syz-executor
 11370  373044  79994      0  3   0x4000080  fsleep        syz-executor
 11370  408598  79994      0  3   0x4000080  fsleep        syz-executor
 15482  452051  49264      0  3        0x80  nanoslp       syz-executor
 15482  473467  49264      0  3   0x4000000  smrbar        syz-executor
 15482   42787  49264      0  3   0x4000080  fsleep        syz-executor
 28153  237327  34044      0  2           0                syz-executor
 28153  182754  34044      0  3   0x4000080  fsleep        syz-executor
 83082  514930      1      0  3        0x82  nanoslp       getty
 63486  121672  79586      0  2       0xc80                syz-executor
 63486  419562  79586      0  3   0x4000080  ttyin         syz-executor
 40202   22410  82138      0  2           0                syz-executor
 40202  384027  82138      0  3   0x4000080  kqread        syz-executor
 40202   34287  82138      0  3   0x4000080  fsleep        syz-executor
 34530   61293      0      0  3     0x14280  nfsidl        nfsio
 87495   61108      0      0  3     0x14280  nfsidl        nfsio
 54600  170733      0      0  3     0x14280  nfsidl        nfsio
 11356  386494      0      0  3     0x14280  nfsidl        nfsio
 47477  159668      0      0  3     0x14280  nfsidl        nfsio
 44318  160806      0      0  3     0x14280  nfsidl        nfsio
 35926  345533      0      0  3     0x14280  nfsidl        nfsio
 15327  311872      0      0  3     0x14280  nfsidl        nfsio
 83458  156457      0      0  3     0x14280  nfsidl        nfsio
 51550  248135      0      0  3     0x14280  nfsidl        nfsio
  7193  481682      0      0  3     0x14280  nfsidl        nfsio
 83004   51855      0      0  3     0x14280  nfsidl        nfsio
 39735  471039      0      0  3     0x14280  nfsidl        nfsio
 99945  260461      0      0  3     0x14280  nfsidl        nfsio
 63478   76317      0      0  3     0x14280  nfsidl        nfsio
 34289  380343      0      0  3     0x14280  nfsidl        nfsio
 43266  124007      0      0  3     0x14280  nfsidl        nfsio
 61191  303341      0      0  3     0x14280  nfsidl        nfsio
 41336  368140      0      0  3     0x14280  nfsidl        nfsio
 20904  405035      0      0  3     0x14280  nfsidl        nfsio
 42870  297742      0      0  3     0x14200  acct          acct
 79586  130439  53230      0  3        0x82  nanoslp       syz-executor
 79994   70097  53230      0  3        0x82  nanoslp       syz-executor
 34044  522929  53230      0  3        0x82  nanoslp       syz-executor
 49264   52624  53230      0  3        0x82  nanoslp       syz-executor
 82138  464299  53230      0  2       0xc82                syz-executor
 31887  136289  53230      0  3        0x82  nanoslp       syz-executor
 92004  483631  53230      0  2         0x2                syz-executor
 26117  316094  53230      0  7         0x2                syz-executor
 53230  115795      1      0  2        0x82                syz-executor
 11822  301756      0      0  3     0x14200  pause         smr
 11651  185842      0      0  2     0x14200                zerothread
 95572  124026      0      0  3     0x14200  aiodoned      aiodoned
 79810  227231      0      0  3     0x14200  syncer        update
 81435  168920      0      0  3     0x14200  cleaner       cleaner
 58267  256118      0      0  3     0x14200  reaper        reaper
 43797  359160      0      0  3     0x14200  pgdaemon      pagedaemon
 74369  347062      0      0  3     0x14200  bored         viomb
 44429   55871      0      0  3  0x40014200  acpi0         acpi0
 89079  176647      0      0  3  0x40014200                idle1
 49103  371290      0      0  3     0x14200  bored         softnet1
  4555  302966      0      0  3     0x14200  bored         softnet0
 40950  364538      0      0  3     0x14200  bored         systqmp
  3355  376453      0      0  3     0x14200  bored         systq
 75649  417573      0      0  3     0x14200  tmoslp        softclockmp
 81529  201906      0      0  3  0x40014200  tmoslp        softclock
 43302  448844      0      0  3  0x40014200                idle0
     1  479061      0      0  3        0x82  wait          init
     0       0     -1      0  3     0x10200  scheduler     swapper
ddb{0}> show all locks
Process 5839 (syz-executor) thread 0xffff8000fffef770 (257671)
exclusive kernel_lock &kernel_lock r = 0 (0xffffffff83aaab00)
#0  witness_lock+0x5f1 stacktrace_save sys/sys/stacktrace.h:37 [inline]
#0  witness_lock+0x5f1 sys/kern/subr_witness.c:1160
#1  unp_connect+0x28c sys/kern/uipc_usrreq.c:872
#2  uipc_dgram_send+0x163 sys/kern/uipc_usrreq.c:609
#3  sosend+0x804 sys/kern/uipc_socket.c:-1
#4  sendit+0x5a5 sys/kern/uipc_syscalls.c:785
#5  sys_sendmsg+0x246 sys/kern/uipc_syscalls.c:603
#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
exclusive rwlock sbufsnd r = 0 (0xffff800010fdf388)
#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  sblock+0xb6 sys/kern/uipc_socket2.c:536
#3  sosend+0x2e9 sys/kern/uipc_socket.c:639
#4  sendit+0x5a5 sys/kern/uipc_syscalls.c:785
#5  sys_sendmsg+0x246 sys/kern/uipc_syscalls.c:603
#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 92004 (syz-executor) thread 0xffff80002a2227d8 (483631)
exclusive rrwlock inode r = 0 (0xfffffd8074e84668)
#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  rrw_enter+0xc6 sys/kern/kern_rwlock.c:621
#3  VOP_LOCK+0xbd sys/kern/vfs_vops.c:527
#4  vn_lock+0xa4 sys/kern/vfs_vnops.c:576
#5  vget+0x2a2 sys/kern/vfs_subr.c:686
#6  cache_lookup+0x351 sys/kern/vfs_cache.c:222
#7  ufs_lookup+0x1e3 sys/ufs/ufs/ufs_lookup.c:160
#8  VOP_LOOKUP+0x6e sys/kern/vfs_vops.c:85
#9  vfs_lookup+0x963 sys/kern/vfs_lookup.c:580
#10 namei+0x7c5 sys/kern/vfs_lookup.c:250
#11 dounlinkat+0xc1 sys/kern/vfs_syscalls.c:1893
#12 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#12 syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
#13 Xsyscall+0x128
Process 26117 (syz-executor) thread 0xffff8000ffffd760 (316094)
exclusive rrwlock inode r = 0 (0xfffffd80757b3ef0)
#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  rrw_enter+0xc6 sys/kern/kern_rwlock.c:621
#3  VOP_LOCK+0xbd sys/kern/vfs_vops.c:527
#4  ufs_ihashins+0x4f ufs_ihash sys/ufs/ufs/ufs_ihash.c:-1 [inline]
#4  ufs_ihashins+0x4f sys/ufs/ufs/ufs_ihash.c:159
#5  ffs_vget+0x187 sys/ufs/ffs/ffs_vfsops.c:1232
#6  ffs_inode_alloc+0x279 sys/ufs/ffs/ffs_alloc.c:393
#7  ufs_mkdir+0xfc sys/ufs/ufs/ufs_vnops.c:1112
#8  VOP_MKDIR+0x101 sys/kern/vfs_vops.c:394
#9  domkdirat+0x179 sys/kern/vfs_syscalls.c:3149
#10 syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#10 syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
#11 Xsyscall+0x128
exclusive rrwlock inode r = 0 (0xfffffd80758a50b0)
#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  rrw_enter+0xc6 sys/kern/kern_rwlock.c:621
#3  VOP_LOCK+0xbd sys/kern/vfs_vops.c:527
#4  vn_lock+0xa4 sys/kern/vfs_vnops.c:576
#5  vfs_lookup+0x12b sys/kern/vfs_lookup.c:431
#6  namei+0x7c5 sys/kern/vfs_lookup.c:250
#7  domkdirat+0x8b sys/kern/vfs_syscalls.c:3134
#8  syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
#8  syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
#9  Xsyscall+0x128
ddb{0}> 

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/23 21:29 openbsd 19a8be4fa5c4 c69befb3 .config console log report [disk image] [bsd.gdb] [kernel image] ci-openbsd-multicore witness: reversal: sbufsnd inode
* Struck through repros no longer work on HEAD.