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From: Paolo Bonzini <pbonzini@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>,
	Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH kernel] KVM: Don't null dereference ops->destroy
Date: Wed, 25 May 2022 09:47:19 +0200	[thread overview]
Message-ID: <4fdbe38d-0e7d-764f-beab-034a9f172137@redhat.com> (raw)
In-Reply-To: <6d291eba-1055-51c3-f015-d029a434b2c0@ozlabs.ru>

On 5/25/22 04:58, Alexey Kardashevskiy wrote:
>>>
> 
> 
> After reading
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2bde9b3ec8bdf60788e9e 
> and neighboring commits, it sounds that each create() should be paired 
> with either destroy() or release() but not necessarily both.

I agree, if release() is implemented then destroy() will never be called 
(except in error situations).

kvm_destroy_devices() should not be touched, except to add a WARN_ON 
perhaps.

> So I'm really not sure dummy handlers is a good idea. Thanks,

But in that case shouldn't kvm_ioctl_create_device also try 
ops->release, i.e.

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6d971fb1b08d..f265e2738d46 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;
  	}

?

Paolo


WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>,
	Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Subject: Re: [PATCH kernel] KVM: Don't null dereference ops->destroy
Date: Wed, 25 May 2022 07:47:19 +0000	[thread overview]
Message-ID: <4fdbe38d-0e7d-764f-beab-034a9f172137@redhat.com> (raw)
In-Reply-To: <6d291eba-1055-51c3-f015-d029a434b2c0@ozlabs.ru>

On 5/25/22 04:58, Alexey Kardashevskiy wrote:
>>>
> 
> 
> After reading
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id+de9b3ec8bdf60788e9e 
> and neighboring commits, it sounds that each create() should be paired 
> with either destroy() or release() but not necessarily both.

I agree, if release() is implemented then destroy() will never be called 
(except in error situations).

kvm_destroy_devices() should not be touched, except to add a WARN_ON 
perhaps.

> So I'm really not sure dummy handlers is a good idea. Thanks,

But in that case shouldn't kvm_ioctl_create_device also try 
ops->release, i.e.

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6d971fb1b08d..f265e2738d46 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;
  	}

?

Paolo

  reply	other threads:[~2022-05-25  7:47 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-24  5:52 [PATCH kernel] KVM: Don't null dereference ops->destroy Alexey Kardashevskiy
2022-05-24  5:52 ` Alexey Kardashevskiy
2022-05-24 20:01 ` Sean Christopherson
2022-05-25  1:52   ` Alexey Kardashevskiy
2022-05-25  1:52     ` Alexey Kardashevskiy
2022-05-25  2:58     ` Alexey Kardashevskiy
2022-05-25  2:58       ` Alexey Kardashevskiy
2022-05-25  7:47       ` Paolo Bonzini [this message]
2022-05-25  7:47         ` Paolo Bonzini
2022-05-31  4:32         ` Alexey Kardashevskiy
2022-05-31  4:32           ` Alexey Kardashevskiy
2022-05-31 17:13           ` Paolo Bonzini
2022-05-31 17:13             ` Paolo Bonzini

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