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

[Colin Ian King <colin.king@canonical.com>]

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.

+
+       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?

Colin