Re: general protection fault in native_write_cr4

[Dmitry Vyukov]

On Tue, Dec 26, 2017 at 9:52 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote:
> On Wed, Dec 20, 2017 at 8:54 AM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote:
>> 2017-12-20 15:49 GMT+08:00 syzbot
>> <bot+ab09454bf4b7a7f8ce7e5e8d97e644d3314a0799@xxxxxxxxxxxxxxxxxxxxxxxxx>:
>>> Hello,
>>>
>>> syzkaller hit the following crash on
>>> f6f3732162b5ae3c771b9285a5a32d72b8586920
>>> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
>>> compiler: gcc (GCC) 7.1.1 20170620
>>> .config is attached
>>> Raw console output is attached.
>>> C reproducer is attached
>>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>>> for information about syzkaller reproducers
>>>
>>>
>>
>> I will have a look again, you continue to run it in kvm guest, right?
>
>
> Our test machines are GCE VMs, so yes, the kernel that catches GPF is
> run as kvm guest.

up

one of top crashers with 50K crashes


>>> kvm: KVM_SET_TSS_ADDR need to be called before entering vcpu
>>> kasan: CONFIG_KASAN_INLINE enabled
>>> kasan: GPF could be caused by NULL-ptr deref or user memory access
>>> general protection fault: 0000 [#1] SMP KASAN
>>> Dumping ftrace buffer:
>>>    (ftrace buffer empty)
>>> Modules linked in:
>>> CPU: 1 PID: 3142 Comm: syzkaller429302 Not tainted 4.15.0-rc3+ #224
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>>> Google 01/01/2011
>>> RIP: 0010:native_write_cr4+0x4/0x10 arch/x86/include/asm/special_insns.h:76
>>> RSP: 0018:ffff8801ca6f75a0 EFLAGS: 00010093
>>> RAX: ffff8801ca1c8700 RBX: 00000000001606e0 RCX: ffffffff811a2a92
>>> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000001606e0
>>> RBP: ffff8801ca6f75a0 R08: 1ffff100394dee0f R09: 0000000000000004
>>> R10: ffff8801ca6f7510 R11: 0000000000000004 R12: 0000000000000093
>>> R13: ffff8801ca1c8700 R14: ffff8801db514850 R15: ffff8801db514850
>>> FS:  0000000001031880(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
>>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>> CR2: 0000000000000000 CR3: 0000000005e22006 CR4: 00000000001626e0
>>> Call Trace:
>>>  __write_cr4 arch/x86/include/asm/paravirt.h:76 [inline]
>>>  __cr4_set arch/x86/include/asm/tlbflush.h:180 [inline]
>>>  cr4_clear_bits arch/x86/include/asm/tlbflush.h:203 [inline]
>>>  kvm_cpu_vmxoff arch/x86/kvm/vmx.c:3582 [inline]
>>>  hardware_disable+0x34a/0x4b0 arch/x86/kvm/vmx.c:3588
>>>  kvm_arch_hardware_disable+0x35/0xd0 arch/x86/kvm/x86.c:7982
>>>  hardware_disable_nolock+0x30/0x40
>>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:3310
>>>  on_each_cpu+0xca/0x1b0 kernel/smp.c:604
>>>  hardware_disable_all_nolock+0x3e/0x50
>>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:3328
>>>  hardware_disable_all arch/x86/kvm/../../../virt/kvm/kvm_main.c:3334
>>> [inline]
>>>  kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:742 [inline]
>>>  kvm_put_kvm+0x956/0xdf0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:755
>>>  kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:766
>>>  __fput+0x327/0x7e0 fs/file_table.c:210
>>>  ____fput+0x15/0x20 fs/file_table.c:244
>>>  task_work_run+0x199/0x270 kernel/task_work.c:113
>>>  exit_task_work include/linux/task_work.h:22 [inline]
>>>  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
>>>  do_group_exit+0x149/0x400 kernel/exit.c:968
>>>  SYSC_exit_group kernel/exit.c:979 [inline]
>>>  SyS_exit_group+0x1d/0x20 kernel/exit.c:977
>>>  entry_SYSCALL_64_fastpath+0x1f/0x96
>>> RIP: 0033:0x441c78
>>> RSP: 002b:00007ffe68e20f68 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
>>> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000441c78
>>> RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
>>> RBP: 00000000006cd018 R08: 00000000000000e7 R09: ffffffffffffffd0
>>> R10: 0000000000000012 R11: 0000000000000246 R12: 0000000000404080
>>> R13: 0000000000404110 R14: 0000000000000000 R15: 0000000000000000
>>> Code: 0f 1f 80 00 00 00 00 55 48 89 e5 0f 20 d8 5d c3 0f 1f 80 00 00 00 00
>>> 55 48 89 e5 0f 22 df 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 <0f> 22 e7 5d c3
>>> 0f 1f 80 00 00 00 00 55 48 89 e5 44 0f 20 c0 5d
>>> RIP: native_write_cr4+0x4/0x10 arch/x86/include/asm/special_insns.h:76 RSP:
>>> ffff8801ca6f75a0
>>> ---[ end trace ca14f0c15b26c251 ]---
>>>
>>>
>>> ---
>>> 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>
>>>
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>>
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