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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88C5BC32773 for ; Fri, 19 Aug 2022 11:25:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348191AbiHSLZy (ORCPT ); Fri, 19 Aug 2022 07:25:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59004 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348610AbiHSLZn (ORCPT ); Fri, 19 Aug 2022 07:25:43 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C65F9FEEB0; Fri, 19 Aug 2022 04:25:42 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4F2BDB8274A; Fri, 19 Aug 2022 11:25:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F579C433D6; Fri, 19 Aug 2022 11:25:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1660908340; bh=jEfI2tZuqE93nCv99untFA824HIB3TeXZACUpILlGqg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=b+8oNnCyF8uwypm+XLZREZu5qAuMbge/xHWWs6983BqVmoXlpWibHGFcsCZIF0ZIG Ds+GSRovsOoSOPNf/qMTUD7bOg7Jz/4IJZOnt3yLGJxfVlqDBAtgbK3O4wh5UYzGOz kU92F0jSvWfSTfaM0BG4qoZ+xsj2bptGI4+07oIE= Date: Fri, 19 Aug 2022 13:25:37 +0200 From: Greg Kroah-Hartman To: Fedor Pchelkin Cc: stable@vger.kernel.org, Tadeusz Struk , Peter Zijlstra , Dietmar Eggemann , linux-kernel@vger.kernel.org, Alexey Khoroshilov , ldv-project@linuxtesting.org, syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com Subject: Re: [PATCH 5.10 1/1] sched/fair: Fix fault in reweight_entity Message-ID: References: <20220819071140.35728-1-pchelkin@ispras.ru> <20220819071140.35728-2-pchelkin@ispras.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220819071140.35728-2-pchelkin@ispras.ru> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 19, 2022 at 10:11:40AM +0300, Fedor Pchelkin wrote: > From: Tadeusz Struk > > commit 13765de8148f71fa795e0a6607de37c49ea5915a upstream. > > Syzbot found a GPF in reweight_entity. This has been bisected to > commit 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid > sched_task_group") > > There is a race between sched_post_fork() and setpriority(PRIO_PGRP) > within a thread group that causes a null-ptr-deref in > reweight_entity() in CFS. The scenario is that the main process spawns > number of new threads, which then call setpriority(PRIO_PGRP, 0, -20), > wait, and exit. For each of the new threads the copy_process() gets > invoked, which adds the new task_struct and calls sched_post_fork() > for it. > > In the above scenario there is a possibility that > setpriority(PRIO_PGRP) and set_one_prio() will be called for a thread > in the group that is just being created by copy_process(), and for > which the sched_post_fork() has not been executed yet. This will > trigger a null pointer dereference in reweight_entity(), as it will > try to access the run queue pointer, which hasn't been set. > > Before the mentioned change the cfs_rq pointer for the task has been > set in sched_fork(), which is called much earlier in copy_process(), > before the new task is added to the thread_group. Now it is done in > the sched_post_fork(), which is called after that. To fix the issue > the remove the update_load param from the update_load param() function > and call reweight_task() only if the task flag doesn't have the > TASK_NEW flag set. > > Fixes: 4ef0c5c6b5ba ("kernel/sched: Fix sched_fork() access an invalid sched_task_group") > Reported-by: syzbot+af7a719bc92395ee41b3@syzkaller.appspotmail.com > Signed-off-by: Tadeusz Struk > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Dietmar Eggemann > Cc: stable@vger.kernel.org > Link: https://lkml.kernel.org/r/20220203161846.1160750-1-tadeusz.struk@linaro.org > Signed-off-by: Fedor Pchelkin > --- > 5.10 adaptation: Replaced a task_struct field '__state' with 'state' Now queued up, thanks. greg k-h