From patchwork Thu May 20 09:19:59 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 444456 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=-19.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 44C8FC43460 for ; Thu, 20 May 2021 09:56:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 282E461C8B for ; Thu, 20 May 2021 09:56:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234748AbhETJ6H (ORCPT ); Thu, 20 May 2021 05:58:07 -0400 Received: from mail.kernel.org ([198.145.29.99]:59520 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234085AbhETJ4F (ORCPT ); Thu, 20 May 2021 05:56:05 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8F70C61429; Thu, 20 May 2021 09:37:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1621503456; bh=P9BN4Rczsk/qoRkcbsB+SQvF4dLql9l84+XijWgXAko=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VvIpS6e+PlLMEKCcW1RlF6bHIbeRZPhy+KbNr77gQJsNSG4+fkXIZaTrqcpUUPB6C G9Oh3FFdS67yfqiEba/wXDDkMdIjqgPqUoOAOG0ts/sQJ9HngT2ngHyHmkxjt/mkEK j1e8HiTp6I2aRzL5CUBt4XoPyi06JDAN7dL3dOns= 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 4.19 230/425] x86/kprobes: Fix to check non boostable prefixes correctly Date: Thu, 20 May 2021 11:19:59 +0200 Message-Id: <20210520092138.995705276@linuxfoundation.org> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210520092131.308959589@linuxfoundation.org> References: <20210520092131.308959589@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 dfc3ab44bc5d..3334e1400345 100644 --- a/arch/x86/kernel/kprobes/core.c +++ b/arch/x86/kernel/kprobes/core.c @@ -170,6 +170,8 @@ 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. */ @@ -182,9 +184,14 @@ 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]; @@ -209,8 +216,8 @@ 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; } }