From 3f1538a4dd00709b1c7f6a4fda31cf5daf4b3e46 Mon Sep 17 00:00:00 2001 From: Jan Kiszka Date: Fri, 18 Sep 2009 20:08:02 -0300 Subject: [PATCH] KVM: x86: Disallow hypercalls for guest callers in rings > 0 (cherry picked from commit 07708c4af1346ab1521b26a202f438366b7bcffd) 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. Signed-off-by: Jan Kiszka Signed-off-by: Avi Kivity Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 6 ++++++ include/linux/kvm_para.h | 1 + 2 files changed, 7 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f0e58397849..e23f5cb3282 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2898,6 +2898,11 @@ 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; @@ -2909,6 +2914,7 @@ 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 3ddce03766c..d73109243fd 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 -- 2.11.4.GIT