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authorJan Kiszka <jan.kiszka@siemens.com>2009-10-07 17:40:32 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2009-10-12 11:33:20 -0700
commitc905930150d0952c4ce008553b377492bcbd29d7 (patch)
tree91fde9a15252018b163295da2e1eb3886b1043a4
parent2578cf95969936c372db29ee2bbc21c9b6a299aa (diff)
KVM: x86: Disallow hypercalls for guest callers in rings > 0 [CVE-2009-3290]
[ backport to 2.6.27 by Chuck Ebbert <cebbert@redhat.com> ] 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 <jan.kiszka@siemens.com> Signed-off-by: Avi Kivity <avi@redhat.com> Cc: Chuck Ebbert <cebbert@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--arch/x86/kvm/x86.c6
-rw-r--r--include/linux/kvm_para.h1
2 files changed, 7 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f7c7142d89ae..60ebfd7eb0cf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2571,6 +2571,11 @@ 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;
@@ -2582,6 +2587,7 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
ret = -KVM_ENOSYS;
break;
}
+out:
vcpu->arch.regs[VCPU_REGS_RAX] = ret;
kvm_x86_ops->decache_regs(vcpu);
++vcpu->stat.hypercalls;
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index 3ddce03766ca..d73109243fda 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