From: Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Dmitry Vyukov" <dvyukov@google.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"KVM list" <kvm@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
"Steve Rutherford" <srutherford@google.com>,
syzkaller <syzkaller@googlegroups.com>
Subject: Re: kvm: use-after-free in complete_emulated_mmio
Date: Mon, 9 Jan 2017 09:38:16 +0800 [thread overview]
Message-ID: <CANRm+CwiZdc18TRG7u7e-0qKip+9-kPzmxB0KUcN6qbmEZhzGA@mail.gmail.com> (raw)
In-Reply-To: <87fcd513-ab71-332c-f78c-a7b77a708764@redhat.com>
2017-01-06 21:37 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>
>
> On 06/01/2017 10:59, Wanpeng Li wrote:
>> 2016-12-27 21:57 GMT+08:00 Dmitry Vyukov <dvyukov@google.com>:
>>> Hello,
>>>
>>> The following program triggers use-after-free in complete_emulated_mmio:
>>> https://gist.githubusercontent.com/dvyukov/79c7ee10f568b0d5c33788534bb6edc9/raw/2c2d4ce0fe86398ed81e65281e8c215c7c3632fb/gistfile1.txt
>>>
>>> BUG: KASAN: use-after-free in complete_emulated_mmio+0x8dd/0xb70
>>> arch/x86/kvm/x86.c:7052 at addr ffff880069f1ed48
>>> Read of size 8 by task syz-executor/31542
>>> CPU: 3 PID: 31542 Comm: syz-executor Not tainted 4.9.0+ #105
>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>>> Call Trace:
>>> check_memory_region+0x139/0x190 mm/kasan/kasan.c:322
>>> memcpy+0x23/0x50 mm/kasan/kasan.c:357
>>> complete_emulated_mmio+0x8dd/0xb70 arch/x86/kvm/x86.c:7052
>>> kvm_arch_vcpu_ioctl_run+0x308d/0x45f0 arch/x86/kvm/x86.c:7090
>>> kvm_vcpu_ioctl+0x673/0x1120 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2569
>>> vfs_ioctl fs/ioctl.c:43 [inline]
>>> do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683
>>> SYSC_ioctl fs/ioctl.c:698 [inline]
>>> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
>>> entry_SYSCALL_64_fastpath+0x1f/0xc2
>>> RIP: 0033:0x4421e9
>>> RSP: 002b:00007f320dc67b58 EFLAGS: 00000286 ORIG_RAX: 0000000000000010
>>> RAX: ffffffffffffffda RBX: 0000000000000018 RCX: 00000000004421e9
>>> RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000018
>>> RBP: 00000000006dbb20 R08: 0000000000000000 R09: 0000000000000000
>>> R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000700000
>>> R13: 00007f320de671c8 R14: 00007f320de69000 R15: 0000000000000000
>>> Object at ffff880069f183c0, in cache kmalloc-16384 size: 16384
>>> Allocated:
>>> PID = 31567
>>> [<ffffffff8123eb36>] save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
>>> [<ffffffff81943353>] save_stack+0x43/0xd0 mm/kasan/kasan.c:502
>>> [<ffffffff8194361a>] set_track mm/kasan/kasan.c:514 [inline]
>>> [<ffffffff8194361a>] kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:605
>>> [<ffffffff8193fa7c>] kmem_cache_alloc_trace+0xec/0x640 mm/slab.c:3629
>>> [<ffffffff810724ce>] kvm_arch_alloc_vm include/linux/slab.h:490 [inline]
>>> [<ffffffff810724ce>] kvm_create_vm
>>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:613 [inline]
>>> [<ffffffff810724ce>] kvm_dev_ioctl_create_vm
>>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:3174 [inline]
>>> [<ffffffff810724ce>] kvm_dev_ioctl+0x1be/0x11b0
>>> arch/x86/kvm/../../../virt/kvm/kvm_main.c:3218
>>> [<ffffffff819af76f>] vfs_ioctl fs/ioctl.c:43 [inline]
>>> [<ffffffff819af76f>] do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:683
>>> [<ffffffff819b0dbf>] SYSC_ioctl fs/ioctl.c:698 [inline]
>>> [<ffffffff819b0dbf>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:689
>>> [<ffffffff83fd1d81>] entry_SYSCALL_64_fastpath+0x1f/0xc2
>>> Memory state around the buggy address:
>>> ffff880069f1ec00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ffff880069f1ec80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>>> ffff880069f1ed00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ^
>>> ffff880069f1ed80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ffff880069f1ee00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>>> ==================================================================
>>>
>>>
>>> On commit e93b1cc8a8965da137ffea0b88e5f62fa1d2a9e6 (Dec 19).
>>>
>>>
>>> I've also printed some values when the bug happens:
>>>
>>> pr_err("vcpu=%p, mmio_fragments=%p frag=%p frag=%d/%d len=%d gpa=%p write=%d\n",
>>> vcpu, vcpu->mmio_fragments, frag, vcpu->mmio_cur_fragment,
>>> vcpu->mmio_nr_fragments, frag->len, (void*)frag->gpa,
>>> vcpu->mmio_is_write);
>>>
>>> [ 26.765898] vcpu=ffff880068590100, mmio_fragments=ffff880068590338
>>> frag=ffff880068590338 frag=0/1 len=152 gpa=0000000000001008 write=1
>>
>>
>> test-2892 [006] .... 118.284172: complete_emulated_mmio: vcpu =
>> ffff9beefb288000, mmio_fragments = ffff9beefb2881b0, frag =
>> ffff9beefb2881b0, frag = 0/1, len = 160, gpa = 0000000000001000, write
>> = 1
>> test-2897 [003] .... 118.284196: complete_emulated_mmio: vcpu =
>> ffff9beef69a0000, mmio_fragments = ffff9beef69a01b0, frag =
>> ffff9beef69a01b0, frag = 0/1, len = 160, gpa = 0000000000001000, write
>> = 1
>>
>> Actually the mmio will be splitted to 8 byte piece and returns to
>> qemu(if it's not emulated by kvm) to be emulated one by one, however,
>> we can observe that there is no subsequent handle to the left pieces,
>> I guess the VM is almost destroyed immediately in the testcase, right?
>
> Hi Wanpeng, yeah, there are only two KVM_RUN. This bug was discussed
> off list and we'll send a patch soon.
Cool, looking forward to your patches. :)
Regards,
Wanpeng Li
prev parent reply other threads:[~2017-01-09 1:38 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-27 13:57 kvm: use-after-free in complete_emulated_mmio Dmitry Vyukov
2017-01-06 9:59 ` Wanpeng Li
2017-01-06 10:16 ` Dmitry Vyukov
2017-01-06 13:37 ` Paolo Bonzini
2017-01-09 1:38 ` Wanpeng Li [this message]
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