From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751712AbdJ1Io4 (ORCPT ); Sat, 28 Oct 2017 04:44:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:58002 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751189AbdJ1Iox (ORCPT ); Sat, 28 Oct 2017 04:44:53 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EC2A218A5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mhiramat@kernel.org Date: Sat, 28 Oct 2017 17:44:49 +0900 From: Masami Hiramatsu To: zhouchengming Cc: Peter Zijlstra , Borislav Petkov , , , , , , , , , , , Subject: Re: [PATCH] kprobes, x86/alternatives: use text_mutex to protect smp_alt_modules Message-Id: <20171028174449.d8c05644c6b2b41326d0527a@kernel.org> In-Reply-To: <59F3DCE0.1080108@huawei.com> References: <1509096884-22993-1-git-send-email-zhouchengming1@huawei.com> <20171027111527.GD1305@nazgul.tnic> <59F31BB5.90905@huawei.com> <20171027123348.GE1305@nazgul.tnic> <20171027141502.GA3165@worktop.lehotels.local> <59F3DCE0.1080108@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 28 Oct 2017 09:26:56 +0800 zhouchengming wrote: > On 2017/10/27 22:15, Peter Zijlstra wrote: > > On Fri, Oct 27, 2017 at 02:33:48PM +0200, Borislav Petkov wrote: > >> On Fri, Oct 27, 2017 at 07:42:45PM +0800, zhouchengming wrote: > >>> This is a real bug happened on one of our machines, below is the calltrace. > >>> We can see the trigger is at alternatives_text_reserved+0x20/0x80, and > >>> encounter a deleted (poisoned) list_head. > >> Looks like some out-of-tree, old kernel thing. We don't have > >> mlx4_stats_sysfs_create() upstream and looking at the boot timestamps, > >> it could be that register_jprobe() is not ready yet. > >> > >> Looking at the Code, though: > >> > >> 20: 74 59 je 0x7b > >> 22: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1) > >> 29: 00 00 > >> 2b:* 48 3b 71 20 cmp 0x20(%rcx),%rsi<-- trapping instruction > >> 2f: 72 3a jb 0x6b > >> 31: 48 3b 79 28 cmp 0x28(%rcx),%rdi > >> 35: 77 34 ja 0x6b > >> > >> %rcx is 0xdead0000000000d0 and that is POISON_POINTER_DELTA + 0xd0 so > >> that looks more like smp_alt_modules is not initialized yet but I could > >> could very well be wrong because this is an old kernel. So trigger that > >> with the upstream kernel without out of tree modules. > > Not to mention that we're about (or just have) yanked jprobes out of the > > kernel entirely. > > Well... but this is a bug of alternatives_text_reserved(), it traverse the list without holding > the smp_alt mutex. So all users of it, like kprobes, will still have this problem. Maybe I could > think of a way to get rid of the mutex entirely. Correct. Peter, this is not related to jprobes, register_kprobe has same issue. Thank you, -- Masami Hiramatsu