Bug the VM if KVM's emulator attempts to inject a bogus exception vector.
The guest is likely doomed even if KVM continues on, and propagating a
bad vector to the rest of KVM runs the risk of breaking other assumptions
in KVM and thus triggering a more egregious bug.
All existing users of emulate_exception() have hardcoded vector numbers
(__load_segment_descriptor() uses a few different vectors, but they're
all hardcoded), and future users are likely to follow suit, i.e. the
change to emulate_exception() is a glorified nop.
As for the ctxt->exception.vector check in x86_emulate_insn(), the few
known times the WARN has been triggered in the past is when the field was
not set when synthesizing a fault, i.e. for all intents and purposes the
check protects against consumption of uninitialized data.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <
20220526210817.
3428868-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int emulate_exception(struct x86_emulate_ctxt *ctxt, int vec,
u32 error, bool valid)
{
- WARN_ON(vec > 0x1f);
+ if (KVM_EMULATOR_BUG_ON(vec > 0x1f, ctxt))
+ return X86EMUL_UNHANDLEABLE;
+
ctxt->exception.vector = vec;
ctxt->exception.error_code = error;
ctxt->exception.error_code_valid = valid;
done:
if (rc == X86EMUL_PROPAGATE_FAULT) {
- WARN_ON(ctxt->exception.vector > 0x1f);
+ if (KVM_EMULATOR_BUG_ON(ctxt->exception.vector > 0x1f, ctxt))
+ return EMULATION_FAILED;
ctxt->have_exception = true;
}
if (rc == X86EMUL_INTERCEPTED)