From: Sean Christopherson Date: Thu, 26 May 2022 21:08:16 +0000 (+0000) Subject: KVM: x86: Bug the VM if the emulator generates a bogus exception vector X-Git-Tag: v6.1-rc5~719^2~6^2~382 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=49a1431d3bea4092082b0082cd9f58f3ccdf57f4;p=platform%2Fkernel%2Flinux-starfive.git KVM: x86: Bug the VM if the emulator generates a bogus exception vector 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 Reviewed-by: Kees Cook Reviewed-by: Vitaly Kuznetsov Message-Id: <20220526210817.3428868-8-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 70a8e0c..2aa1746 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -624,7 +624,9 @@ static unsigned long seg_base(struct x86_emulate_ctxt *ctxt, int seg) 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; @@ -5728,7 +5730,8 @@ writeback: 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)