From nobody Fri Apr 10 23:24:21 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9946BC32774 for ; Thu, 18 Aug 2022 16:14:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344336AbiHRQOW (ORCPT ); Thu, 18 Aug 2022 12:14:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344144AbiHRQOO (ORCPT ); Thu, 18 Aug 2022 12:14:14 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 93D3F474DC for ; Thu, 18 Aug 2022 09:14:13 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 2E393B8221D for ; Thu, 18 Aug 2022 16:14:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5C2F1C43140; Thu, 18 Aug 2022 16:14:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660839250; bh=LklsORKu6eLoWSUy8Uv/91SX4T5e2aOeczaluthpBWw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=QsLszNJ3f2L4nbyCqD+5T07lURvGYi6AVA/5VggLdyEV1znUd7o2KRiNvSKgubRPF nUOYJT7odSMOSfU7PwwLh8FLzhTn1ZiaGtsfyfbjc3ziYqk1Henxd0ayZ4MRhKwZXr LbyJH7Z2KbA8ImR+YhkLDQ2NLZk8v53CQRUtEGty3e98Nac8Cp6OblMaOj4Gdv+BYB Y6cO4/kxUgInyOR8eEmYSaijciZUak64MSmrapVdjQ0U5xW2RE9KJIqyIQ8d8RR/47 pECRO4NzhNWnVIs3GxzYpkZKc2JmexHOwJ5TAL/7ynmPSXbtjCEsCqMcbs1Iaiwczw 1yi9o5fJwAbhQ== From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Pengfei Xu , "Yang, Weijiang" , "Su, Heng" , Peter Zijlstra , Paolo Bonzini Subject: [PATCH 3/3] x86/kvm: Fix "missing ENDBR" BUG for fastop functions Date: Thu, 18 Aug 2022 08:53:43 -0700 Message-Id: <0d4116f90e9d0c1b754bb90c585e6f0415a1c508.1660837839.git.jpoimboe@kernel.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" The following BUG was reported: traps: Missing ENDBR: andw_ax_dx+0x0/0x10 [kvm] ------------[ cut here ]------------ kernel BUG at arch/x86/kernel/traps.c:253! invalid opcode: 0000 [#1] PREEMPT SMP NOPTI asm_exc_control_protection+0x2b/0x30 RIP: 0010:andw_ax_dx+0x0/0x10 [kvm] Code: c3 cc cc cc cc 0f 1f 44 00 00 66 0f 1f 00 48 19 d0 c3 cc cc cc cc 0f 1f 40 00 f3 0f 1e fa 20 d0 c3 cc cc cc cc 0f 1f 44 00 00 <66> 0f 1f 00 66 21 d0 c3 cc cc cc cc 0f 1f 40 00 66 0f 1f 00 21 d0 ? andb_al_dl+0x10/0x10 [kvm] ? fastop+0x5d/0xa0 [kvm] x86_emulate_insn+0x822/0x1060 [kvm] x86_emulate_instruction+0x46f/0x750 [kvm] complete_emulated_mmio+0x216/0x2c0 [kvm] kvm_arch_vcpu_ioctl_run+0x604/0x650 [kvm] kvm_vcpu_ioctl+0x2f4/0x6b0 [kvm] ? wake_up_q+0xa0/0xa0 The BUG occurred because the ENDBR in the andw_ax_dx() fastop function had been incorrectly "sealed" (converted to a NOP) by apply_ibt_endbr(). Objtool marked it to be sealed because KVM has no compile-time references to the function. Instead KVM calculates its address at runtime. Prevent objtool from annotating fastop functions as sealable by creating throwaway dummy compile-time references to the functions. Fixes: 6649fa876da4 ("x86/ibt,kvm: Add ENDBR to fastops") Reported-by: Pengfei Xu Debugged-by: Peter Zijlstra Signed-off-by: Josh Poimboeuf --- arch/x86/kvm/emulate.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 205d566ebd72..f092c54d1a2f 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -326,7 +326,8 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop= _t fop); ".align " __stringify(FASTOP_SIZE) " \n\t" \ ".type " name ", @function \n\t" \ name ":\n\t" \ - ASM_ENDBR + ASM_ENDBR \ + IBT_NOSEAL(name) =20 #define FOP_FUNC(name) \ __FOP_FUNC(#name) --=20 2.37.2