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From: butt3rflyh4ck <butterflyhuangxx@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Woodhouse, David" <dwmw@amazon.co.uk>,
	kvm@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: There is a null-ptr-deref bug in kvm_dirty_ring_get in virt/kvm/dirty_ring.c
Date: Mon, 8 Nov 2021 13:11:57 +0800	[thread overview]
Message-ID: <CAFcO6XMe9RXRHxbjXoNBE3xFaATJggrpiRH-9127XBrBzf3eeg@mail.gmail.com> (raw)
In-Reply-To: <9eb83cdd-9314-0d1f-0d4b-0cf4432e1e84@redhat.com>

Hi, No one pays attention to this issue?

Regards,
  butt3rflyh4ck.

On Fri, Oct 22, 2021 at 4:08 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 18/10/21 19:14, butt3rflyh4ck wrote:
> > {
> > struct kvm_vcpu *vcpu = kvm_get_running_vcpu();  //-------> invoke
> > kvm_get_running_vcpu() to get a vcpu.
> >
> > WARN_ON_ONCE(vcpu->kvm != kvm); [1]
> >
> > return &vcpu->dirty_ring;
> > }
> > ```
> > but we had not called KVM_CREATE_VCPU ioctl to create a kvm_vcpu so
> > vcpu is NULL.
>
> It's not just because there was no call to KVM_CREATE_VCPU; in general
> kvm->dirty_ring_size only works if all writes are associated to a
> specific vCPU, which is not the case for the one of
> kvm_xen_shared_info_init.
>
> David, what do you think?  Making dirty-page ring buffer incompatible
> with Xen is ugly and I'd rather avoid it; taking the mutex for vcpu 0 is
> not an option because, as the reporter said, you might not have even
> created a vCPU yet when you call KVM_XEN_HVM_SET_ATTR.  The remaining
> option would be just "do not mark the page as dirty if the ring buffer
> is active".  This is feasible because userspace itself has passed the
> shared info gfn; but again, it's ugly...
>
> Paolo
>


-- 
Active Defense Lab of Venustech

  parent reply	other threads:[~2021-11-08  5:12 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-18 17:14 butt3rflyh4ck
2021-10-21 20:08 ` Paolo Bonzini
2021-10-28  7:42   ` butt3rflyh4ck
2021-11-08  5:11   ` butt3rflyh4ck [this message]
2021-11-16 15:41   ` butt3rflyh4ck
2021-11-16 16:22   ` [EXTERNAL] " David Woodhouse
2021-11-16 17:07     ` David Woodhouse
2021-11-17  9:46   ` Woodhouse, David
2021-11-17 16:49     ` Paolo Bonzini
2021-11-17 18:10       ` Woodhouse, David
2021-11-20 10:16   ` KVM: Warn if mark_page_dirty() is called without an active vCPU David Woodhouse
2021-11-22 17:01     ` Sean Christopherson
2021-11-22 17:52       ` David Woodhouse
2021-11-22 18:49         ` Sean Christopherson
2022-01-13 12:06     ` Christian Borntraeger
2022-01-13 12:14       ` Paolo Bonzini
2022-01-13 12:29         ` [PATCH] KVM: avoid warning on s390 in mark_page_dirty Christian Borntraeger
2022-01-13 12:31           ` David Woodhouse
2022-01-18  8:37           ` Christian Borntraeger
2022-01-18  8:44             ` Paolo Bonzini
2022-01-18  8:53               ` Christian Borntraeger
2022-01-18 11:44                 ` Paolo Bonzini
2022-01-13 12:30         ` KVM: Warn if mark_page_dirty() is called without an active vCPU David Woodhouse
2022-01-13 12:51           ` Christian Borntraeger
2022-01-13 13:22             ` David Woodhouse
2022-01-13 15:09               ` Christian Borntraeger
2022-01-13 14:36           ` Paolo Bonzini

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