From: Jan Kiszka [ backport to 2.6.27 by Chuck Ebbert ] commit 07708c4af1346ab1521b26a202f438366b7bcffd upstream. 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 Cc: Chuck Ebbert Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 6 ++++++ include/linux/kvm_para.h | 1 + 2 files changed, 7 insertions(+) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2571,6 +2571,11 @@ int kvm_emulate_hypercall(struct kvm_vcp 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; @@ -2582,6 +2587,7 @@ int kvm_emulate_hypercall(struct kvm_vcp ret = -KVM_ENOSYS; break; } +out: vcpu->arch.regs[VCPU_REGS_RAX] = ret; kvm_x86_ops->decache_regs(vcpu); ++vcpu->stat.hypercalls; --- 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 linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/