linux-kernel - Re: [Qemu-devel] kvm bug in __rmap_clear

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Message-ID: <7fdf2551-3d55-1bd9-2848-720a880cc93e@redhat.com>
Date:   Fri, 24 Feb 2017 16:14:03 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Chris Friesen <chris.friesen@...driver.com>,
        "Herongguang (Stephen)" <herongguang.he@...wei.com>,
        "Han, Huaitong" <huaitong.han@...el.com>,
        "hangaohuai@...wei.com" <hangaohuai@...wei.com>,
        stable@...r.kernel.org
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "fangying1@...wei.com" <fangying1@...wei.com>,
        "xudong.hao@...ux.intel.com" <xudong.hao@...ux.intel.com>,
        "qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
        "wangxinxin.wang@...wei.com" <wangxinxin.wang@...wei.com>,
        "kai.huang@...ux.intel.com" <kai.huang@...ux.intel.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "guangrong.xiao@...ux.intel.com" <guangrong.xiao@...ux.intel.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [Qemu-devel] kvm bug in __rmap_clear_dirty during live migration



On 24/02/2017 16:10, Chris Friesen wrote:
> On 02/23/2017 08:23 PM, Herongguang (Stephen) wrote:
> 
>> On 2017/2/22 22:43, Paolo Bonzini wrote:
> 
>>> Hopefully Gaohuai and Rongguang can help with this too.
>>>
>>> Paolo
>>
>> Yes, we are looking into and testing this.
>>
>> I think this can result in any memory corruption, if VM1 writes its
>> PML buffer into VM2’s VMCS (since sched_in/sched_out notifier of VM1
>> is not registered yet), then VM1 is destroyed (hence its PML buffer
>> is freed back to kernel), after that, VM2 starts migration, so CPU
>> logs VM2’s dirty GFNS into a freed memory, results in any memory
>> corruption.
>>
>> As its severity, this commit
>> (http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4e59516a12a6ef6dcb660cb3a3f70c64bd60cfec)
>>
>> is eligible to back port to kernel stable.
> 
> Are we expecting that fix to resolve the original issue, or is it a
> separate issue that needs fixing in stable?

It should be the original issue.

Paolo