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=-5.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS autolearn=no 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 BBFC5C433E2 for ; Fri, 28 Aug 2020 14:19:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8C6EA208CA for ; Fri, 28 Aug 2020 14:19:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598624366; bh=TdetsC/IwhbsAgTlgvX2TtgjuiEy6W6tBp2ZWqLO+JM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=b+zevFymEAYOnZ4qhr331ebtcqt4gaZHXx8aEs8oUf9g7oqb+XhWsKK+grDWmBb9S NyaJkzZjVScMHQhaTNWMc1SsedCu0ZuasvI0y4xnDlKzurHtvILAC3tvUqwbJMUL0W SGuJrkdzlZtE/IwDvmu2BHE4ugoaMQ20tQ+DYlyw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726307AbgH1OTZ (ORCPT ); Fri, 28 Aug 2020 10:19:25 -0400 Received: from mail.kernel.org ([198.145.29.99]:39898 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725857AbgH1OTY (ORCPT ); Fri, 28 Aug 2020 10:19:24 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (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 2F8C7208C9; Fri, 28 Aug 2020 14:19:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598624364; bh=TdetsC/IwhbsAgTlgvX2TtgjuiEy6W6tBp2ZWqLO+JM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qtDWadleCxTR0PpV04LVMcmFE6CLPUIAXMPQ01N15drNu1lbMIvXC65zqFQ4kp6WG Gih9hip23BkPOqD3sY/i9NgFZUnQ4gf7g6v8tnpXSS6aADVP/GRRdhKXlEEGBEWqzg NL6VQLuwsWmPZ96IL+h1DpTYX02OGeYN7drBGqkk= Date: Fri, 28 Aug 2020 23:19:20 +0900 From: Masami Hiramatsu To: peterz@infradead.org Cc: "Eddy_Wu@trendmicro.com" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "davem@davemloft.net" , "rostedt@goodmis.org" , "naveen.n.rao@linux.ibm.com" , "anil.s.keshavamurthy@intel.com" , "linux-arch@vger.kernel.org" , "cameron@moodycamel.com" , "oleg@redhat.com" , "will@kernel.org" , "paulmck@kernel.org" Subject: Re: [RFC][PATCH 3/7] kprobes: Remove kretprobe hash Message-Id: <20200828231920.4cb817dd9c624703ecfedc5d@kernel.org> In-Reply-To: <20200828135824.GD1362448@hirez.programming.kicks-ass.net> References: <20200827161237.889877377@infradead.org> <20200827161754.359432340@infradead.org> <7df0a1af432040d9908517661c32dc34@trendmicro.com> <20200828225113.9541a5f67a3bcb17c4ce930c@kernel.org> <20200828135824.GD1362448@hirez.programming.kicks-ass.net> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Fri, 28 Aug 2020 15:58:24 +0200 peterz@infradead.org wrote: > On Fri, Aug 28, 2020 at 10:51:13PM +0900, Masami Hiramatsu wrote: > > > OK, schedule function will be the key. I guess the senario is.. > > > > 1) kretporbe replace the return address with kretprobe_trampoline on task1's kernel stack > > 2) the task1 forks task2 before returning to the kretprobe_trampoline > > 3) while copying the process with the kernel stack, task2->kretprobe_instances.first = NULL > > 4) task2 returns to the kretprobe_trampoline > > 5) Bomb! > > > > Hmm, we need to fixup the kernel stack when copying process. > > How would that scenario have been avoided in the old code? Because there > task2 would have a different has and not have found a kretprobe_instance > either. Good question, I think this bug has not been solved in old code too. Let me check. Thanks, -- Masami Hiramatsu