From: Paolo Bonzini <pbonzini@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>, kvm@vger.kernel.org
Cc: kvm-ppc@vger.kernel.org, Sean Christopherson <seanjc@google.com>
Subject: Re: [PATCH kernel v2] KVM: Don't null dereference ops->destroy
Date: Wed, 01 Jun 2022 10:28:50 +0000 [thread overview]
Message-ID: <d507c4d0-d1b3-adef-8081-64b8b6ee33ae@redhat.com> (raw)
In-Reply-To: <20220601014328.1444271-1-aik@ozlabs.ru>
On 6/1/22 03:43, Alexey Kardashevskiy wrote:
> A KVM device cleanup happens in either of two callbacks:
> 1) destroy() which is called when the VM is being destroyed;
> 2) release() which is called when a device fd is closed.
>
> Most KVM devices use 1) but Book3s's interrupt controller KVM devices
> (XICS, XIVE, XIVE-native) use 2) as they need to close and reopen during
> the machine execution. The error handling in kvm_ioctl_create_device()
> assumes destroy() is always defined which leads to NULL dereference as
> discovered by Syzkaller.
>
> This adds a checks for destroy!=NULL and adds a missing release().
>
> This is not changing kvm_destroy_devices() as devices with defined
> release() should have been removed from the KVM devices list by then.
>
> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Queued, thanks.
Paolo
> ---
> Changes:
> v2:
> * do not touch kvm_destroy_devices
> * call release() in the error path
> ---
> virt/kvm/kvm_main.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index f30bb8c16f26..e1c4bca95040 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4299,8 +4299,11 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
> kvm_put_kvm_no_destroy(kvm);
> mutex_lock(&kvm->lock);
> list_del(&dev->vm_node);
> + if (ops->release)
> + ops->release(dev);
> mutex_unlock(&kvm->lock);
> - ops->destroy(dev);
> + if (ops->destroy)
> + ops->destroy(dev);
> return ret;
> }
>
Queued, thanks.
Paolo
prev parent reply other threads:[~2022-06-01 10:28 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-01 1:43 [PATCH kernel v2] KVM: Don't null dereference ops->destroy Alexey Kardashevskiy
2022-06-01 10:28 ` Paolo Bonzini [this message]
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