On 08/03/2009 04:47 PM, Jan Kiszka wrote:
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@xxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 8 ++++++++
include/linux/kvm_para.h | 1 +
2 files changed, 9 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2539e9a..966d309 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3190,6 +3190,7 @@ static inline gpa_t hc_gpa(struct kvm_vcpu *vcpu, unsigned long a0,
int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
{
unsigned long nr, a0, a1, a2, a3, ret;
+ struct kvm_segment cs;
int r = 1;
nr = kvm_register_read(vcpu, VCPU_REGS_RAX);
@@ -3208,6 +3209,12 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
a3&= 0xFFFFFFFF;
}
+ kvm_get_segment(vcpu,&cs, VCPU_SREG_CS);
+ if (cs.dpl != 0) {
+ ret = -KVM_EPERM;
+ goto out;
+ }
+
I think kvm_x86_ops->get_cpl() is more accurate (and we can optimize it
to avoid a ton of vmcs_read()s).
--
error compiling committee.c: too many arguments to function
--
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