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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 5EA15C432C0 for ; Fri, 29 Nov 2019 17:57:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 30B7B2176D for ; Fri, 29 Nov 2019 17:57:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575050279; bh=vJOOfAq3Itw/Da/jBhb+gwC+mqd4jGT+yyfYWoBfvIg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Ck1ML46JKr7Qrq0eZigGt2VC/ZJ2jzo3H2jEqmRZouMGF7xoa6Iu/UP9RM3y24FUM XiIMN6wzjo31yeKQtjyo0S1iw43OhwdGLjwSlOoxWfDfvNlV8Ng02bT1v3WLY8ehuF BaY32JzyN9UHGfQ5pxCj3vv5H+Cn1bA/lkqM5pv4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727149AbfK2R56 (ORCPT ); Fri, 29 Nov 2019 12:57:58 -0500 Received: from mail.kernel.org ([198.145.29.99]:49010 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727146AbfK2R56 (ORCPT ); Fri, 29 Nov 2019 12:57:58 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (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 48EF52158A; Fri, 29 Nov 2019 17:57:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1575050277; bh=vJOOfAq3Itw/Da/jBhb+gwC+mqd4jGT+yyfYWoBfvIg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JiaaasDmwLWpaT4HcbZdvzWAQu8WbCJzug4hwNE77iy5qXSzcwV+Q4WEPEji8woKM 16Y3mO9CSK4VZuH2Yy0p7rEkVqWMOd+J/y4Z55Nv6AwyBWJUvdT4Z4/wdLEn1A9zfS woNgtdfkmeLyXqNGiNE+a/+uTg++rjz5fTfK2xF4= Date: Fri, 29 Nov 2019 17:57:53 +0000 From: Will Deacon To: Christian Brauner Cc: linux-kernel@vger.kernel.org, bsingharora@gmail.com, dvyukov@google.com, elver@google.com, parri.andrea@gmail.com, stable@vger.kernel.org, syzbot+c5d03165a1bd1dead0c1@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH v6] taskstats: fix data-race Message-ID: <20191129175752.GB29789@willie-the-truck> References: <20191009114809.8643-1-christian.brauner@ubuntu.com> <20191021113327.22365-1-christian.brauner@ubuntu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191021113327.22365-1-christian.brauner@ubuntu.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Oct 21, 2019 at 01:33:27PM +0200, Christian Brauner wrote: > When assiging and testing taskstats in taskstats_exit() there's a race > when writing and reading sig->stats when a thread-group with more than > one thread exits: > > cpu0: > thread catches fatal signal and whole thread-group gets taken down > do_exit() > do_group_exit() Nit: I don't think this is the signal-handling path. > taskstats_exit() > taskstats_tgid_alloc() > The tasks reads sig->stats without holding sighand lock. > > cpu1: > task calls exit_group() > do_exit() > do_group_exit() Nit: These ^^ seem to be the wrong way round. Will