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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 B78C4C43331 for ; Tue, 24 Mar 2020 13:16:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FCB6208D5 for ; Tue, 24 Mar 2020 13:16:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585055810; bh=OGv4NJMH6egSO3CM+oM4/EP7ikbuiFpvtEs66GSlFxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=LnINfbR7UOK5kJShCcAlFqdpHb7cT0Bl55OpUTWtqp16RqKdjWwef25nXkaK7tagQ WMJXZBdlYinaopEiop2krdDdN65owgM9WBdaqkBbl1xJmo2BGrhoBMjOWh9PngMDiy 8rekRBJ5lBh39ckS6PnUSyEKz2U2ov2YXWuoPmQE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728071AbgCXNQt (ORCPT ); Tue, 24 Mar 2020 09:16:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:36364 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727755AbgCXNQr (ORCPT ); Tue, 24 Mar 2020 09:16:47 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 0DCA420775; Tue, 24 Mar 2020 13:16:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585055806; bh=OGv4NJMH6egSO3CM+oM4/EP7ikbuiFpvtEs66GSlFxA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DrSFie3XAyKWVovOa6ruKIm7D47K1YvwahT3gP/AAZZ0Ykj0eca7bWcDlkKho84Nw ZBYAAbhDuHRzntopNoJ1RWNZMqt6xTvJGNGfBXZnHzJm3xx7LEUE/OEozz3Gn3MqCp ZcaFUn3dvnWPZsdb4wSARYvc4c/cXIFZkQ0pfL34= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kwon Je Oh , Carlo Nonato , Paolo Valente , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 033/102] block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group() Date: Tue, 24 Mar 2020 14:10:25 +0100 Message-Id: <20200324130810.126577787@linuxfoundation.org> X-Mailer: git-send-email 2.25.2 In-Reply-To: <20200324130806.544601211@linuxfoundation.org> References: <20200324130806.544601211@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 d0e36d6522649..86cd718e0380b 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -593,12 +593,13 @@ 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