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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 534DACA9EB9 for ; Wed, 23 Oct 2019 18:06:03 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 258E92173B for ; Wed, 23 Oct 2019 18:06:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 258E92173B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BE4706B0006; Wed, 23 Oct 2019 14:06:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B94566B0007; Wed, 23 Oct 2019 14:06:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A82A56B0008; Wed, 23 Oct 2019 14:06:02 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0160.hostedemail.com [216.40.44.160]) by kanga.kvack.org (Postfix) with ESMTP id 829146B0006 for ; Wed, 23 Oct 2019 14:06:02 -0400 (EDT) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id 1CDBF5DFC for ; Wed, 23 Oct 2019 18:06:02 +0000 (UTC) X-FDA: 76075828164.24.iron92_8bf020ea9065f X-HE-Tag: iron92_8bf020ea9065f X-Filterd-Recvd-Size: 3556 Received: from Galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by imf28.hostedemail.com (Postfix) with ESMTP for ; Wed, 23 Oct 2019 18:06:01 +0000 (UTC) Received: from p5b06da22.dip0.t-ipconnect.de ([91.6.218.34] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iNL1A-0006gN-7Y; Wed, 23 Oct 2019 20:05:56 +0200 Date: Wed, 23 Oct 2019 20:05:49 +0200 (CEST) From: Thomas Gleixner To: Cyrill Gorcunov cc: LKML , Ingo Molnar , Peter Zijlstra , linux-mm@kvack.org, Catalin Marinas , x86@kernel.org, Josh Poimboeuf Subject: [PATCH] x86/dumpstack/64: Don't evaluate exception stacks before setup In-Reply-To: <20191023135943.GK12121@uranus.lan> Message-ID: References: <20191019114421.GK9698@uranus.lan> <20191022142325.GD12121@uranus.lan> <20191022145619.GE12121@uranus.lan> <20191023135943.GK12121@uranus.lan> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Cyrill reported the following crash: BUG: unable to handle page fault for address: 0000000000001ff0 #PF: supervisor read access in kernel mode RIP: 0010:get_stack_info+0xb3/0x148 It turns out that if the stack tracer is invoked before the exception stack mappings are initialized in_exception_stack() can erroneously classify an invalid address as an address inside of an exception stack: begin = this_cpu_read(cea_exception_stacks); <- 0 end = begin + sizeof(exception stacks); i.e. any address between 0 and end will be considered as exception stack address and the subsequent code will then try to derefence the resulting stack frame at a non mapped address. end = begin + (unsigned long)ep->size; ==> end = 0x2000 regs = (struct pt_regs *)end - 1; ==> regs = 0x2000 - sizeof(struct pt_regs *) = 0x1ff0 info->next_sp = (unsigned long *)regs->sp; ==> Crashes due to accessing 0x1ff0 Prevent this by checking the validity of the cea_exception_stack base address and bailing out if it is zero. Fixes: afcd21dad88b ("x86/dumpstack/64: Use cpu_entry_area instead of orig_ist") Reported-by: Cyrill Gorcunov Signed-off-by: Thomas Gleixner Tested-by: Cyrill Gorcunov Cc: stable@vger.kernel.org --- arch/x86/kernel/dumpstack_64.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/arch/x86/kernel/dumpstack_64.c +++ b/arch/x86/kernel/dumpstack_64.c @@ -94,6 +94,13 @@ static bool in_exception_stack(unsigned BUILD_BUG_ON(N_EXCEPTION_STACKS != 6); begin = (unsigned long)__this_cpu_read(cea_exception_stacks); + /* + * Handle the case where stack trace is collected _before_ + * cea_exception_stacks had been initialized. + */ + if (!begin) + return false; + end = begin + sizeof(struct cea_exception_stacks); /* Bail if @stack is outside the exception stack area. */ if (stk < begin || stk >= end)