Re: WARNING in x86_emulate_insn

[Jim Mattson]

Try disabling the module parameter, "unrestricted_guest." Make sure
that the module parameter, "emulate_invalid_guest_state" is enabled.
This combination allows userspace to feed invalid guest state into the
in-kernel emulator.

On Thu, Dec 7, 2017 at 2:40 AM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
> 2017-12-07 15:52 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>:
>> 2017-12-07 15:49 GMT+08:00 èåå <lantianyu1986@xxxxxxxxx>:
>>> Hi Dmitry:
>>>      I tried to reproduce the issue via syz-execprog with attached
>>> reproducer on latest linux-next but it causes VM-entry failure due to
>>> invalid guest state...
>>
>> Because rflags is 0 in his program. You can set ept=0 and retry.
>
> In addition, you can apply this commit
> https://lkml.org/lkml/2017/12/7/144 before testing.
>
>>
>> Regards,
>> Wanpeng Li
>>
>>>
>>> 2017-12-07 14:25 GMT+08:00 Dmitry Vyukov <dvyukov@xxxxxxxxxx>:
>>>> On Thu, Dec 7, 2017 at 1:44 AM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
>>>>> 2017-12-06 4:07 GMT+08:00 syzbot
>>>>> <bot+75375385991b4f8c599704a10849863c586ea284@xxxxxxxxxxxxxxxxxxxxxxxxx>:
>>>>>> Hello,
>>>>>>
>>>>>> syzkaller hit the following crash on
>>>>>> fb20eb9d798d2f4c1a75b7fe981d72dfa8d7270d
>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>>>>>> compiler: gcc (GCC) 7.1.1 20170620
>>>>>> .config is attached
>>>>>> Raw console output is attached.
>>>>>>
>>>>>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>>>>> for information about syzkaller reproducers
>>>>>>
>>>>>
>>>>> Is there a c program to reproduce?
>>>>
>>>> No, syzbot does not hide reproducers. See the referenced doc for
>>>> details: https://github.com/google/syzkaller/blob/master/docs/syzbot.md#syzkaller-reproducers
>>>>
>>>>
>>>>> Regards,
>>>>> Wanpeng Li
>>>>>
>>>>>>
>>>>>> kvm: KVM_SET_TSS_ADDR need to be called before entering vcpu
>>>>>> WARNING: CPU: 1 PID: 3526 at arch/x86/kvm/emulate.c:5654
>>>>>> x86_emulate_insn+0xd01/0x3cf0 arch/x86/kvm/emulate.c:5654
>>>>>> Kernel panic - not syncing: panic_on_warn set ...
>>>>>>
>>>>>> CPU: 1 PID: 3526 Comm: syz-executor4 Not tainted 4.15.0-rc1-next-20171201+
>>>>>> #57
>>>>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>>>>> Google 01/01/2011
>>>>>> Call Trace:
>>>>>>  __dump_stack lib/dump_stack.c:17 [inline]
>>>>>>  dump_stack+0x194/0x257 lib/dump_stack.c:53
>>>>>>  panic+0x1e4/0x41c kernel/panic.c:183
>>>>>>  __warn+0x1dc/0x200 kernel/panic.c:547
>>>>>>  report_bug+0x211/0x2d0 lib/bug.c:184
>>>>>>  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:177
>>>>>>  fixup_bug arch/x86/kernel/traps.c:246 [inline]
>>>>>>  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:295
>>>>>>  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:314
>>>>>>  invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1066
>>>>>> RIP: 0010:x86_emulate_insn+0xd01/0x3cf0 arch/x86/kvm/emulate.c:5654
>>>>>> RSP: 0018:ffff8801d0fff3e8 EFLAGS: 00010293
>>>>>> RAX: ffff8801d17b60c0 RBX: 1ffff1003a1ffe86 RCX: ffffffff81154351
>>>>>> RDX: 0000000000000000 RSI: ffffffffffffffff RDI: ffff8801d0b5b5c8
>>>>>> RBP: ffff8801d0fff4f8 R08: ffff8801d0b58d80 R09: ffffffff85224da0
>>>>>> R10: 0000000000000001 R11: ffffed003a16b6d4 R12: 00000000000000ff
>>>>>> R13: ffff8801d0b5b5a0 R14: 0000000000000002 R15: ffff8801d0b5b6c3
>>>>>>  x86_emulate_instruction+0x411/0x1ad0 arch/x86/kvm/x86.c:5771
>>>>>>  emulate_instruction arch/x86/include/asm/kvm_host.h:1164 [inline]
>>>>>>  complete_emulated_io arch/x86/kvm/x86.c:7190 [inline]
>>>>>>  complete_emulated_pio+0xdd/0x1b0 arch/x86/kvm/x86.c:7201
>>>>>>  kvm_arch_vcpu_ioctl_run+0x2db2/0x5c60 arch/x86/kvm/x86.c:7305
>>>>>>  kvm_vcpu_ioctl+0x64c/0x1010 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2574
>>>>>>  vfs_ioctl fs/ioctl.c:46 [inline]
>>>>>>  do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
>>>>>>  SYSC_ioctl fs/ioctl.c:701 [inline]
>>>>>>  SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
>>>>>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>>>>>> RIP: 0033:0x4529d9
>>>>>> RSP: 002b:00007f6b6b2d5c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000010
>>>>>> RAX: ffffffffffffffda RBX: 0000000000758020 RCX: 00000000004529d9
>>>>>> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000004
>>>>>> RBP: 000000000000039b R08: 0000000000000000 R09: 0000000000000000
>>>>>> R10: 0000000000000000 R11: 0000000000000212 R12: 00000000006f2728
>>>>>> R13: 00000000ffffffff R14: 00007f6b6b2d66d4 R15: 0000000000000000
>>>>>> Dumping ftrace buffer:
>>>>>>    (ftrace buffer empty)
>>>>>> Kernel Offset: disabled
>>>>>> Rebooting in 86400 seconds..
>>>>>>
>>>>>>
>>>>>> ---
>>>>>> This bug is generated by a dumb bot. It may contain errors.
>>>>>> See https://goo.gl/tpsmEJ for details.
>>>>>> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
>>>>>> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
>>>>>>
>>>>>> syzbot will keep track of this bug report.
>>>>>> Once a fix for this bug is committed, please reply to this email with:
>>>>>> #syz fix: exact-commit-title
>>>>>> If you want to test a patch for this bug, please reply with:
>>>>>> #syz test: git://repo/address.git branch
>>>>>> and provide the patch inline or as an attachment.
>>>>>> To mark this as a duplicate of another syzbot report, please reply with:
>>>>>> #syz dup: exact-subject-of-another-report
>>>>>> If it's a one-off invalid bug report, please reply with:
>>>>>> #syz invalid
>>>>>> Note: if the crash happens again, it will cause creation of a new bug
>>>>>> report.
>>>>>> Note: all commands must start from beginning of the line in the email body.
>>>>>
>>>>> --
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>>>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>>
>>>
>>> --
>>> Best regards
>>> Tianyu Lan