From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v1] KVM: kvm_io_bus_unregister_dev() should never fail
Date: Thu, 23 Mar 2017 17:20:48 +0100
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References: <20170323143441.5749-1-david@redhat.com>
 <20170323170635.1fb91a2c.cornelia.huck@de.ibm.com>
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Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        rkrcmar@redhat.com, Dmitry Vyukov <dvyukov@google.com>,
        Marcelo Tosatti <mtosatti@redhat.com>, stable@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
To: Cornelia Huck <cornelia.huck@de.ibm.com>
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> As this may set kvm->buses[bus_idx] to NULL, don't you also need to
> guard for bus == NULL in kvm_io_bus_destroy()? (I looked at the code on
> kvm/queue.)

very right, so something like this?

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e1be4b4..ef1aa7f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -728,7 +728,8 @@ static void kvm_destroy_vm(struct kvm *kvm)
        spin_unlock(&kvm_lock);
        kvm_free_irq_routing(kvm);
        for (i = 0; i < KVM_NR_BUSES; i++) {
-               kvm_io_bus_destroy(kvm->buses[i]);
+               if (kvm->buses[i])
+                       kvm_io_bus_destroy(kvm->buses[i]);
                kvm->buses[i] = NULL;
        }
        kvm_coalesced_mmio_free(kvm);

Thanks!

> 
>>  	synchronize_srcu_expedited(&kvm->srcu);
>>  	kfree(bus);
>> -	return r;
>> +	return;
>>  }
> 


-- 

Thanks,

David