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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 C18C4C10F29 for ; Mon, 16 Mar 2020 02:36:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9628A206BE for ; Mon, 16 Mar 2020 02:36:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326207; bh=dmhLfHVWp2qxWaMfTfJhVl2xwkEquJBqtbaqRq3rT9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Xrd2lXSch6STsQx7VC3SNxcleEs+NuepfL/T7OFOBj3/+TxCgFf1ZY43xugzfVCC6 +2btKFEv7Mx/KKC6oEdbvfctOfpLr/KrLIxOwSogLY8Q27GMETwTn7mVDn58ngsJdh n/8BP7j3vBY5hwiOqy1KMIjQyQsTH34GAkhOG664= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729563AbgCPCgq (ORCPT ); Sun, 15 Mar 2020 22:36:46 -0400 Received: from mail.kernel.org ([198.145.29.99]:40214 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730209AbgCPCfh (ORCPT ); Sun, 15 Mar 2020 22:35:37 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AEBE5206BE; Mon, 16 Mar 2020 02:35:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326136; bh=dmhLfHVWp2qxWaMfTfJhVl2xwkEquJBqtbaqRq3rT9Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H7irpbZZ8zoDCNCKihJNxZV/WNM9+OJMHIA8VPk9LXWNRx6GCQ4pQ9HYrke3JCfeV J312G/mZ3+Dlf/u3GhAOeI19SRdYDll3GY19swbv1aQspcVlXGaW8pYQUQXpA6UIQR qLWpsFxBN6O+ykVSlw43tITwtJNluGIu82JsO7qA= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Carlo Nonato , Kwon Je Oh , Paolo Valente , Jens Axboe , Sasha Levin , cgroups@vger.kernel.org, linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.14 14/15] block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group() Date: Sun, 15 Mar 2020 22:35:18 -0400 Message-Id: <20200316023519.2050-14-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200316023519.2050-1-sashal@kernel.org> References: <20200316023519.2050-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Carlo Nonato [ Upstream commit 14afc59361976c0ba39e3a9589c3eaa43ebc7e1d ] The bfq_find_set_group() function takes as input a blkcg (which represents a cgroup) and retrieves the corresponding bfq_group, then it updates the bfq internal group hierarchy (see comments inside the function for why this is needed) and finally it returns the bfq_group. In the hierarchy update cycle, the pointer holding the correct bfq_group that has to be returned is mistakenly used to traverse the hierarchy bottom to top, meaning that in each iteration it gets overwritten with the parent of the current group. Since the update cycle stops at root's children (depth = 2), the overwrite becomes a problem only if the blkcg describes a cgroup at a hierarchy level deeper than that (depth > 2). In this case the root's child that happens to be also an ancestor of the correct bfq_group is returned. The main consequence is that processes contained in a cgroup at depth greater than 2 are wrongly placed in the group described above by BFQ. This commits fixes this problem by using a different bfq_group pointer in the update cycle in order to avoid the overwrite of the variable holding the original group reference. Reported-by: Kwon Je Oh Signed-off-by: Carlo Nonato Signed-off-by: Paolo Valente Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/bfq-cgroup.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c index afbbe5750a1f8..7d7aee024ece2 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -499,12 +499,13 @@ struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, */ entity = &bfqg->entity; for_each_entity(entity) { - bfqg = container_of(entity, struct bfq_group, entity); - if (bfqg != bfqd->root_group) { - parent = bfqg_parent(bfqg); + struct bfq_group *curr_bfqg = container_of(entity, + struct bfq_group, entity); + if (curr_bfqg != bfqd->root_group) { + parent = bfqg_parent(curr_bfqg); if (!parent) parent = bfqd->root_group; - bfq_group_set_parent(bfqg, parent); + bfq_group_set_parent(curr_bfqg, parent); } } -- 2.20.1