syzbot

login: uvm_fault(0xfffffd8078f0c3d8, 0x98, 0, 1) -> e
fatal page fault in supervisor mode
trap type 6 code 0 rip ffffffff828aa368 cs 8 rflags 10246 cr2 98 cpl 0 rsp ffff800037fad9f0
gsbase 0xffff8000299adff0  kgsbase 0x0
panic: trap type 6, code=0, pc=ffffffff828aa368
Starting stack trace...
panic(ffffffff834812fb) at panic+0x1d0 sys/kern/subr_prf.c:229
kerntrap(ffff800037fad940) at kerntrap+0x30b
alltraps_kern_meltdown() at alltraps_kern_meltdown+0x7b
dovutimens(ffff8000fffefca0,fffffd8067a9aeb0,ffff800037fadb20) at dovutimens+0x368 sys/kern/vfs_syscalls.c:2771
sys_futimes(ffff8000fffefca0,ffff800037fadc70,ffff800037fadbc0) at sys_futimes+0x208 sys/kern/vfs_syscalls.c:2813
syscall(ffff800037fadc70) at syscall+0xb17 mi_syscall sys/sys/syscall_mi.h:176 [inline]
syscall(ffff800037fadc70) at syscall+0xb17 sys/arch/amd64/amd64/trap.c:783
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0xe681c4df40, count: 250
End of stack trace.
WARNING: SPL NOT LOWERED ON SYSCALL 12 1884056480 EXIT 0 4
Stopped at      savectx+0xae:   movl    $0,%gs:0x688
    TID    PID    UID     PRFLAGS     PFLAGS  CPU  COMMAND
*125269  86069      0           0          0    1  syz-executor
 233713  19265      0           0          0    0  syz-executor
savectx() at savectx+0xae
end of kernel
end trace frame: 0x720e704c6c40, count: 14
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}> set $lines = 0
ddb{1}> set $maxwidth = 0
ddb{1}> show panic
*cpu1: uvm_fault(0xfffffd8078f0c3d8, 0x98, 0, 1) -> e
ddb{1}> trace
savectx() at savectx+0xae
end of kernel
end trace frame: 0x720e704c6c40, count: -1
ddb{1}> show registers
rdi                                0
rsi                                0
rbp               0xffff80003bbc11e0
rbx                                0
rdx                                0
rcx               0xffff8000fffeed10
rax                             0x3b
r8                0xffff80003bbc1110
r9                               0x1
r10               0x425f241683362076
r11               0x54915a1e38a3893b
r12                                0
r13                                0
r14               0xffff8000fffeed10
r15                                0
rip               0xffffffff819633ee    savectx+0xae
cs                               0x8
rflags                          0x46
rsp               0xffff80003bbc1160
ss                              0x10
savectx+0xae:   movl    $0,%gs:0x688
ddb{1}> show proc
PROC (syz-executor) tid=125269 pid=86069 tcnt=1 stat=onproc
    flags process=0 proc=0
    runpri=50, usrpri=50, slppri=17, nice=20
    wchan=0x0, wmesg=, ps_single=0x0 scnt=0 ecnt=0
    forw=0xffffffffffffffff, list=0xffff8000fffefca0,0xffffffff83a05250
    process=0xffff80002a38eb68 user=0xffff80003bbbc000, vmspace=0xfffffd8078f0cd60
    estcpu=36, cpticks=1, pctcpu=0.0, user=0, sys=1, intr=0
ddb{1}> ps
   PID     TID   PPID    UID  S       FLAGS  WAIT          COMMAND
*86069  125269  66178      0  7           0                syz-executor
 19265  233713  26610      0  7           0                syz-executor
 19265  251308  26610      0  3   0x4000000  sbar          syz-executor
 13570  268881  69132      0  2    0x100002                sh
 13026  243400  87137      0  2           0                syz-executor
 13026  206996  87137      0  3   0x4000080  fsleep        syz-executor
 64706  481078  88880      0  2           0                syz-executor
 98200  355737  10814      0  2           0                syz-executor
 69132  376207  40540      0  3        0x82  wait          syz-executor
  9229  519416      1      0  3    0x100083  ttyin         getty
 76895  341610      0      0  3     0x14200  acct          acct
 85611  472746  40540      0  3        0x82  piperd        syz-executor
 87137  355940  40540      0  3        0x82  nanoslp       syz-executor
 66178  361577  40540      0  3        0x82  nanoslp       syz-executor
 65334  474663  40540      0  2         0x2                syz-executor
 88880  277105  40540      0  3        0x82  nanoslp       syz-executor
 26610    6014  40540      0  3        0x82  nanoslp       syz-executor
 10814  288021  40540      0  3        0x82  nanoslp       syz-executor
 40540  462080      1      0  2         0x2                syz-executor
 28290  291887      1     74  3   0x1100092  bpf           pflogd
 58114  253528      1     73  3   0x1100090  kqread        syslogd
 38312   23669      0      0  3     0x14200  bored         smr
 35749  483851      0      0  2     0x14200