From: Jan Kiszka <[email protected]> So far unprivileged guest callers running in ring 3 can issue, e.g., MMU hypercalls. Normally, such callers cannot provide any hand-crafted MMU command structure as it has to be passed by its physical address, but they can still crash the guest kernel by passing random addresses.
To close the hole, this patch considers hypercalls valid only if issued from guest ring 0. This may still be relaxed on a per-hypercall base in the future once required. Cc: [email protected] Signed-off-by: Jan Kiszka <[email protected]> Signed-off-by: Avi Kivity <[email protected]> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index b407d3c..93bee07 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3209,6 +3209,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) a3 &= 0xFFFFFFFF; } + if (kvm_x86_ops->get_cpl(vcpu) != 0) { + ret = -KVM_EPERM; + goto out; + } + switch (nr) { case KVM_HC_VAPIC_POLL_IRQ: ret = 0; @@ -3220,6 +3225,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) ret = -KVM_ENOSYS; break; } +out: kvm_register_write(vcpu, VCPU_REGS_RAX, ret); ++vcpu->stat.hypercalls; return r; diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h index 3ddce03..d731092 100644 --- a/include/linux/kvm_para.h +++ b/include/linux/kvm_para.h @@ -13,6 +13,7 @@ #define KVM_ENOSYS 1000 #define KVM_EFAULT EFAULT #define KVM_E2BIG E2BIG +#define KVM_EPERM EPERM #define KVM_HC_VAPIC_POLL_IRQ 1 #define KVM_HC_MMU_OP 2 -- To unsubscribe from this list: send the line "unsubscribe kvm-commits" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
