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Subject[PATCH 3/3] KVM: X86: Don't report L2 emulation failures to user-space
Date
This patch prevents that emulation failures which result
from emulating an instruction for an L2-Guest results in
being reported to userspace.
Without this patch a malicious L2-Guest would be able to
kill the L1 by triggering a race-condition between an vmexit
and the instruction emulator.
With this patch the L2 will most likely only kill itself in
this situation.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
arch/x86/kvm/x86.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 410d2d1..78329dd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4320,13 +4320,19 @@ EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt);

static int handle_emulation_failure(struct kvm_vcpu *vcpu)
{
+ int r = EMULATE_DONE;
+
++vcpu->stat.insn_emulation_fail;
trace_kvm_emulate_insn_failed(vcpu);
- vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
- vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
- vcpu->run->internal.ndata = 0;
+ if (!kvm_vcpu_is_gm(vcpu)) {
+ vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
+ vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
+ vcpu->run->internal.ndata = 0;
+ r = EMULATE_FAIL;
+ }
kvm_queue_exception(vcpu, UD_VECTOR);
- return EMULATE_FAIL;
+
+ return r;
}

static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva)
--
1.7.1



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