linux-kernel - Re: [PATCH v2 5/6] KVM: x86: prevent setup of invalid routes

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Date:   Tue, 10 Jan 2017 13:26:48 +0800
From:   Peter Xu <peterx@...hat.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 5/6] KVM: x86: prevent setup of invalid routes

On Fri, Dec 16, 2016 at 04:10:05PM +0100, Radim Krčmář wrote:
> The check in kvm_set_pic_irq() and kvm_set_ioapic_irq() was just a
> temporary measure until the code improved enough for us to do this.
> 
> This changes APIC in a case when KVM_SET_GSI_ROUTING is called to set up pic
> and ioapic routes before KVM_CREATE_IRQCHIP.  Those rules would get overwritten
> by KVM_CREATE_IRQCHIP at best, so it is pointless to allow it.  Userspaces
> hopefully noticed that things don't work if they do that and don't do that.
> 
> Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>

Since we are at here, do we need to protect KVM_SET_GSI_ROUTING in
general as well to make sure kernel APIC is there? Like:

---------8<---------

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 482612b..31141a7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3057,6 +3057,10 @@ static long kvm_vm_ioctl(struct file *filp,
                struct kvm_irq_routing_entry *entries = NULL;

                r = -EFAULT;
+
+               if (!irqchip_in_kernel(kvm))
+                       goto out;
+
                if (copy_from_user(&routing, argp, sizeof(routing)))
                        goto out;
                r = -EINVAL;

--------->8---------

Thanks,

-- peterx