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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,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 7117DC433DF for ; Sun, 18 Oct 2020 19:18:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 344B522282 for ; Sun, 18 Oct 2020 19:18:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603048698; bh=lCZKQ7KGG1SLMxrz/BobWDhhT068d+17W29g9IlqiF0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=DuqFA+LC+zoTAEO0s/cklCcsviDxgEd5XVd5LfbmyTPLgYkvKBLNb8IXEVMSVQfn0 nXODn3XnzMuwLX7PinJLQSiALEd/bwIcO6aMh2HqmhWp1g1NUKcKhCdy55o/tlapUK RThDje+R7oupNd2BHyIYDWcjAJ3CUYLUoCHhk9Xw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727385AbgJRTSR (ORCPT ); Sun, 18 Oct 2020 15:18:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:56062 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727326AbgJRTSM (ORCPT ); Sun, 18 Oct 2020 15:18:12 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id F181322282; Sun, 18 Oct 2020 19:18:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603048691; bh=lCZKQ7KGG1SLMxrz/BobWDhhT068d+17W29g9IlqiF0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=SLSfiWbvmPDLzneNjApmzG3wb+404D6EoMvA82jL3UDZ3sKHMvoKTdXmsWWOGjuZB YIYThbO5BXyWC7ujKXsWXRNVtVTBjYaeQoxP4HWZgbFiS2d180TZVxWbsgIuvXfT8F blRAIfCqcxW9++quH+ktsxJ/fGCBmYKByLRtC3rA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mark Mossberg , Borislav Petkov , Sasha Levin Subject: [PATCH AUTOSEL 5.9 003/111] x86/dumpstack: Fix misleading instruction pointer error message Date: Sun, 18 Oct 2020 15:16:19 -0400 Message-Id: <20201018191807.4052726-3-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201018191807.4052726-1-sashal@kernel.org> References: <20201018191807.4052726-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore 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