From: Christoffer Dall Date: Tue, 3 Jul 2018 20:54:14 +0000 (+0200) Subject: KVM: arm/arm64: Fix vgic init race X-Git-Tag: v4.19-rc1~55^2~12^2~29 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=1d47191de7e15900f8fbfe7cccd7c6e1c2d7c31a;p=thirdparty%2Fkernel%2Flinux.git KVM: arm/arm64: Fix vgic init race The vgic_init function can race with kvm_arch_vcpu_create() which does not hold kvm_lock() and we therefore have no synchronization primitives to ensure we're doing the right thing. As the user is trying to initialize or run the VM while at the same time creating more VCPUs, we just have to refuse to initialize the VGIC in this case rather than silently failing with a broken VCPU. Reviewed-by: Eric Auger Signed-off-by: Christoffer Dall Signed-off-by: Marc Zyngier --- diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c index 2673efce65f34..b714179137414 100644 --- a/virt/kvm/arm/vgic/vgic-init.c +++ b/virt/kvm/arm/vgic/vgic-init.c @@ -271,6 +271,10 @@ int vgic_init(struct kvm *kvm) if (vgic_initialized(kvm)) return 0; + /* Are we also in the middle of creating a VCPU? */ + if (kvm->created_vcpus != atomic_read(&kvm->online_vcpus)) + return -EBUSY; + /* freeze the number of spis */ if (!dist->nr_spis) dist->nr_spis = VGIC_NR_IRQS_LEGACY - VGIC_NR_PRIVATE_IRQS;