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KVM: Don't null dereference ops->destroy 

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Alexey Kardashevskiy 2022-06-01 03:43:28 +02:00 committed by Paolo Bonzini
parent ffd1925a59
commit e8bc242701
1 changed files with 4 additions and 1 deletions
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5
virt/kvm/kvm_main.c
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@ -4300,8 +4300,11 @@ 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;
}