From mboxrd@z Thu Jan 1 00:00:00 1970 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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 452B4C55178 for ; Tue, 27 Oct 2020 16:34:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1E6A21655 for ; Tue, 27 Oct 2020 16:34:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603816467; bh=lCZKQ7KGG1SLMxrz/BobWDhhT068d+17W29g9IlqiF0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZTTUtAuoEd5pCD3ozo4os5ZTRPo93eIo6wpJz7eb+W9JhS/pK21GwJ98PgBq4ypY9 nESr34SYt0nI+/PgtDyC8NpayOz7leZbF1PzJ9SoZ8mMqCfQ0oqKnirdlq3z9ChKcv WdizeJ1ln+YI+koYvmdq5iQ88uKqG+vSeecIQAsw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1810175AbgJ0QeY (ORCPT ); Tue, 27 Oct 2020 12:34:24 -0400 Received: from mail.kernel.org ([198.145.29.99]:49544 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1802461AbgJ0Psv (ORCPT ); Tue, 27 Oct 2020 11:48:51 -0400 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C374822265; Tue, 27 Oct 2020 15:48:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603813729; bh=lCZKQ7KGG1SLMxrz/BobWDhhT068d+17W29g9IlqiF0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ivlwTxGueFAE+TH1Yuq6qnfKpMozSNCn93lXeYETpIHgc2bUm+gJw1hUr/O9dD+sr JwDPDn26jDCF4ugK2f22RB65IcjKq3R+DXsRpSoGf6I8dRuECyOc72nS3se2DYnhl4 QiOqpO0JgvTEoCQz/RPGkVaA+sRIGSGA8yl85oMI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Mark Mossberg , Borislav Petkov , Sasha Levin Subject: [PATCH 5.9 643/757] x86/dumpstack: Fix misleading instruction pointer error message Date: Tue, 27 Oct 2020 14:54:53 +0100 Message-Id: <20201027135520.731919820@linuxfoundation.org> X-Mailer: git-send-email 2.29.1 In-Reply-To: <20201027135450.497324313@linuxfoundation.org> References: <20201027135450.497324313@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mark Mossberg [ Upstream commit 238c91115cd05c71447ea071624a4c9fe661f970 ] Printing "Bad RIP value" if copy_code() fails can be misleading for userspace pointers, since copy_code() can fail if the instruction pointer is valid but the code is paged out. This is because copy_code() calls copy_from_user_nmi() for userspace pointers, which disables page fault handling. This is reproducible in OOM situations, where it's plausible that the code may be reclaimed in the time between entry into the kernel and when this message is printed. This leaves a misleading log in dmesg that suggests instruction pointer corruption has occurred, which may alarm users. Change the message to state the error condition more precisely. [ bp: Massage a bit. ] Signed-off-by: Mark Mossberg Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201002042915.403558-1-mark.mossberg@gmail.com Signed-off-by: Sasha Levin --- arch/x86/kernel/dumpstack.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 48ce44576947c..ea8d51ec251bb 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -115,7 +115,8 @@ void show_opcodes(struct pt_regs *regs, const char *loglvl) unsigned long prologue = regs->ip - PROLOGUE_SIZE; if (copy_code(regs, opcodes, prologue, sizeof(opcodes))) { - printk("%sCode: Bad RIP value.\n", loglvl); + printk("%sCode: Unable to access opcode bytes at RIP 0x%lx.\n", + loglvl, prologue); } else { printk("%sCode: %" __stringify(PROLOGUE_SIZE) "ph <%02x> %" __stringify(EPILOGUE_SIZE) "ph\n", loglvl, opcodes, -- 2.25.1