From patchwork Wed May 12 14:48:37 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "gregkh@linuxfoundation.org" X-Patchwork-Id: 437174 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3CAF7C43603 for ; Wed, 12 May 2021 15:04:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F28136193F for ; Wed, 12 May 2021 15:04:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232098AbhELPFb (ORCPT ); Wed, 12 May 2021 11:05:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:58748 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232503AbhELPDO (ORCPT ); Wed, 12 May 2021 11:03:14 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 00D6E616E8; Wed, 12 May 2021 14:58:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1620831505; bh=wwIhF2xAuSV55HP7yrdE0V0hfvVgJOdEKKN2w/RSf8A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=xXP1+QJeFvt0l5rFMeD9v/Vn4L660EGLT7NkLqmZFArthMq2V4dFJc7XnMmGXh+zJ Z4jm0tPblvwwY/c6p8Kcv35x5CNfzL0S6X0aX8vm55XH3ZWmosT87ZqYY0zgYv6ss0 yH1j4BWK38oQE34tpUfeLJ8GutCyzMI9aANQDv1M= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Masami Hiramatsu , Ingo Molnar , Sasha Levin Subject: [PATCH 5.4 146/244] x86/kprobes: Fix to check non boostable prefixes correctly Date: Wed, 12 May 2021 16:48:37 +0200 Message-Id: <20210512144747.680436015@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210512144743.039977287@linuxfoundation.org> References: <20210512144743.039977287@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Masami Hiramatsu [ Upstream commit 6dd3b8c9f58816a1354be39559f630cd1bd12159 ] There are 2 bugs in the can_boost() function because of using x86 insn decoder. Since the insn->opcode never has a prefix byte, it can not find CS override prefix in it. And the insn->attr is the attribute of the opcode, thus inat_is_address_size_prefix( insn->attr) always returns false. Fix those by checking each prefix bytes with for_each_insn_prefix loop and getting the correct attribute for each prefix byte. Also, this removes unlikely, because this is a slow path. Fixes: a8d11cd0714f ("kprobes/x86: Consolidate insn decoder users for copying code") Signed-off-by: Masami Hiramatsu Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/161666691162.1120877.2808435205294352583.stgit@devnote2 Signed-off-by: Sasha Levin --- arch/x86/kernel/kprobes/core.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c index 5294018535d0..c205d77d57da 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -157,6 +157,8 @@ NOKPROBE_SYMBOL(skip_prefixes); int can_boost(struct insn *insn, void *addr) { kprobe_opcode_t opcode; + insn_byte_t prefix; + int i; if (search_exception_tables((unsigned long)addr)) return 0; /* Page fault may occur on this address. */ @@ -169,9 +171,14 @@ int can_boost(struct insn *insn, void *addr) if (insn->opcode.nbytes != 1) return 0; - /* Can't boost Address-size override prefix */ - if (unlikely(inat_is_address_size_prefix(insn->attr))) - return 0; + for_each_insn_prefix(insn, i, prefix) { + insn_attr_t attr; + + attr = inat_get_opcode_attribute(prefix); + /* Can't boost Address-size override prefix and CS override prefix */ + if (prefix == 0x2e || inat_is_address_size_prefix(attr)) + return 0; + } opcode = insn->opcode.bytes[0]; @@ -196,8 +203,8 @@ int can_boost(struct insn *insn, void *addr) /* clear and set flags are boostable */ return (opcode == 0xf5 || (0xf7 < opcode && opcode < 0xfe)); default: - /* CS override prefix and call are not boostable */ - return (opcode != 0x2e && opcode != 0x9a); + /* call is not boostable */ + return opcode != 0x9a; } }