Re: KVM: Introduce a 'release' method for KVM devices

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 02/05/2019 00:42, Colin Ian King wrote:
> Hi,
> 
> Static analysis with Coverity picked up an issue in the following commit:
> 
> commit 2bde9b3ec8bdf60788e9e2ce8c07a2f8d6003dbd
> Author: Cédric Le Goater <clg@kaod.org>
> Date:   Thu Apr 18 12:39:41 2019 +0200
> 
>     KVM: Introduce a 'release' method for KVM devices
> 
> 
>         struct kvm *kvm = dev->kvm;
> 
> +       if (!dev)
> +               return -ENODEV;
> 
> If dev is null then the dereference of dev->kvm when assigning pointer
> kvm will cause an null pointer dereference.  This is easily fixed by
> assigning kvm after the dev null check.

Yes, this is a bug.

> 
> +
> +       if (dev->kvm != kvm)
> +               return -EPERM;
> 
> I don't understand the logic of the above check. kvm is the same
> dev->kvm on the earlier assignment, so dev->kvm != kvm seems to be
> always false, so this check seems to be redundant. Am I missing
> something more fundamental here?

Nope. This looks like unfortunate cut-n-paste which slipped through out
reviewing process :-D


-- 
Alexey