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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,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 2FCCEC47247 for ; Fri, 1 May 2020 02:01:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0D37F20873 for ; Fri, 1 May 2020 02:01:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588298472; bh=TGng++haxmjKEAxWTDMCt+me7RqYg/DPhKnyheMa2+E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=DHpBClIgG1Dj9CClgrZEq9hYvH93Cn9aoWk7L32EKDIQoipR/atfYRQn3gHiD5AEm mVxmXBkZLV0Ih5fXqiotZnRabGlV5eEt1Wgg1NbY6VFe4MQ9/8+K6vFQhDYEfw2lIX aQQ/2xyygaAVCDDCqH3hVBuZ6YpnmxD0zHyOBHns= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728070AbgEACBL (ORCPT ); Thu, 30 Apr 2020 22:01:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:55950 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727889AbgEACBL (ORCPT ); Thu, 30 Apr 2020 22:01:11 -0400 Received: from devnote (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 E21AB2073E; Fri, 1 May 2020 02:01:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1588298470; bh=TGng++haxmjKEAxWTDMCt+me7RqYg/DPhKnyheMa2+E=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=URt7r82KCUw4/FpnlqtLK2lwwbKBKLoUccNmriUdGhHDebv21eK1bGHH6DTwRa128 67HmXFSGYmNdy9h3gS+T/kIStuMRe1Ls0QxtGSuGO8srfn4PuYocXspwYHUfUQhOXN IYRTXGNcySptZupssYgZE9jnS/sJ9dUIFhp/12iY= Date: Fri, 1 May 2020 11:01:07 +0900 From: Masami Hiramatsu To: Ingo Molnar , Ingo Molnar Cc: Jiri Olsa , Jiri Olsa , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Peter Zijlstra , lkml , "bibo,mao" , "Ziqian SUN (Zamir)" , stable@vger.kernel.org Subject: Re: [PATCHv2] kretprobe: Prevent triggering kretprobe from within kprobe_flush_task Message-Id: <20200501110107.bc859c6603704c0bcdb8889a@kernel.org> In-Reply-To: <20200428213627.GI1476763@krava> References: <20200409184451.GG3309111@krava> <20200409201336.GH3309111@krava> <20200410093159.0d7000a08fd76c2eaf1398f8@kernel.org> <20200414160338.GE208694@krava> <20200415090507.GG208694@krava> <20200416105506.904b7847a1b621b75463076d@kernel.org> <20200416091320.GA322899@krava> <20200416224250.7a53fb581e50aa32df75a0cf@kernel.org> <20200416143104.GA400699@krava> <20200417163810.ffe5c9145eae281fc493932c@kernel.org> <20200428213627.GI1476763@krava> X-Mailer: Sylpheed 3.5.1 (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-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Apr 2020 23:36:27 +0200 Jiri Olsa wrote: > On Fri, Apr 17, 2020 at 04:38:10PM +0900, Masami Hiramatsu wrote: > > SNIP > > > > > > > The code within the kretprobe handler checks for probe reentrancy, > > > so we won't trigger any _raw_spin_lock_irqsave probe in there. > > > > > > The problem is in outside kprobe_flush_task, where we call: > > > > > > kprobe_flush_task > > > kretprobe_table_lock > > > raw_spin_lock_irqsave > > > _raw_spin_lock_irqsave > > > > > > where _raw_spin_lock_irqsave triggers the kretprobe and installs > > > kretprobe_trampoline handler on _raw_spin_lock_irqsave return. > > > > > > The kretprobe_trampoline handler is then executed with already > > > locked kretprobe_table_locks, and first thing it does is to > > > lock kretprobe_table_locks ;-) the whole lockup path like: > > > > > > kprobe_flush_task > > > kretprobe_table_lock > > > raw_spin_lock_irqsave > > > _raw_spin_lock_irqsave ---> probe triggered, kretprobe_trampoline installed > > > > > > ---> kretprobe_table_locks locked > > > > > > kretprobe_trampoline > > > trampoline_handler > > > kretprobe_hash_lock(current, &head, &flags); <--- deadlock > > > > > > Adding kprobe_busy_begin/end helpers that mark code with fake > > > probe installed to prevent triggering of another kprobe within > > > this code. > > > > > > Using these helpers in kprobe_flush_task, so the probe recursion > > > protection check is hit and the probe is never set to prevent > > > above lockup. > > > > > > > Thanks Jiri! > > > > Ingo, could you pick this up? > > Ingo, any chance you could take this one? Hi Ingo, Should I make a pull request for all kprobes related patches to you? Thank you, -- Masami Hiramatsu