linux-kernel - Re: WARNING in x86_emulate

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Message-ID: <CANRm+Cz7YT==PeEq6LRJvD+W0ye3-Hd_+XFmX2CTD-e_x=7q4w@mail.gmail.com>
Date:   Thu, 7 Dec 2017 18:40:35 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     蓝天宇 <lantianyu1986@...il.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot 
        <bot+75375385991b4f8c599704a10849863c586ea284@...kaller.appspotmail.com>,
        "H. Peter Anvin" <hpa@...or.com>, kvm <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        syzkaller-bugs@...glegroups.com,
        Thomas Gleixner <tglx@...utronix.de>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: WARNING in x86_emulate_insn

2017-12-07 15:52 GMT+08:00 Wanpeng Li <kernellwp@...il.com>:
> 2017-12-07 15:49 GMT+08:00 蓝天宇 <lantianyu1986@...il.com>:
>> 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@...gle.com>:
>>> On Thu, Dec 7, 2017 at 1:44 AM, Wanpeng Li <kernellwp@...il.com> wrote:
>>>> 2017-12-06 4:07 GMT+08:00 syzbot
>>>> <bot+75375385991b4f8c599704a10849863c586ea284@...kaller.appspotmail.com>:
>>>>> 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@...glegroups.com.
>>>>> Please credit me with: Reported-by: syzbot <syzkaller@...glegroups.com>
>>>>>
>>>>> 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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>>
>>
>>
>> --
>> Best regards
>> Tianyu Lan