Am 15.03.2017 um 07:24 schrieb Peter Xu: > On Tue, Mar 14, 2017 at 02:34:29PM +0100, David Hildenbrand wrote: >> Avoid races between KVM_SET_GSI_ROUTING and KVM_CREATE_IRQCHIP by taking >> the kvm->lock when setting up routes. >> >> If KVM_CREATE_IRQCHIP fails, KVM_SET_GSI_ROUTING could have already set >> up routes pointing at pic/ioapic, being silently removed already. >> >> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> >> --- >> virt/kvm/kvm_main.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c >> index a17d787..ad0f8b2 100644 >> --- a/virt/kvm/kvm_main.c >> +++ b/virt/kvm/kvm_main.c >> @@ -3079,8 +3079,11 @@ static long kvm_vm_ioctl(struct file *filp, >> routing.nr * sizeof(*entries))) >> goto out_free_irq_routing; >> } >> + /* avoid races with KVM_CREATE_IRQCHIP on x86 */ >> + mutex_lock(&kvm->lock); >> r = kvm_set_irq_routing(kvm, entries, routing.nr, >> routing.flags); >> + mutex_unlock(&kvm->lock); >> out_free_irq_routing: >> vfree(entries); >> break; >> -- >> 2.9.3 >> > > Out of my curiousity: do we have a use case that these two operations > might collapse (KVM_CREATE_IRQCHIP and KVM_SET_GSI_ROUTING)? Or is > this patch only for the sake of security? Just for the sake of security. I think, in general such calls are not supposed to be done in parallel. But of course, user space can. > > Another thing to mention is that, I guess adding this lock will > benefit KVM_CAP_SPLIT_IRQCHIP as well, maybe nice to mention it too in > the commit message. No worth a repost for this single reason though. > I added "Also, as a side effect, this patch makes sure that KVM_SET_GSI_ROUTING and KVM_CAP_SPLIT_IRQCHIP cannot run in parallel." Thanks! > Thanks, > > -- peterx > -- Thanks, David
