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=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 6247EC10DCE for ; Mon, 16 Mar 2020 02:37:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37BE0206EB for ; Mon, 16 Mar 2020 02:37:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326258; bh=Qb3WFXji45qyPaTvm2PnxhbwUJAHncNwwNgYzamZ68Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=lUvoDPMl9iQfl90Gvz1uYQlB41s7WAMtQlYl6mC40V1y4LFKatC1ObofeFz9vLQwo 4s2e+amGOlolHRGfbMKZeEzKdLC9v07kytXJw45fux2HSAySByFxTOf46L9viFVsnK jDuLc3sGlK0IuGu2w+ukVJ8UznNNWW7sGd3HOFlM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730315AbgCPChd (ORCPT ); Sun, 15 Mar 2020 22:37:33 -0400 Received: from mail.kernel.org ([198.145.29.99]:39572 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730120AbgCPCfR (ORCPT ); Sun, 15 Mar 2020 22:35:17 -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 4EEDE2072A; Mon, 16 Mar 2020 02:35:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1584326117; bh=Qb3WFXji45qyPaTvm2PnxhbwUJAHncNwwNgYzamZ68Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oNqpx6BBB7i1Le3J8uIKkaPuhDpE8hptxsfpykuG2lFAt7jooPJ4O8pHF6zCWr9k3 EcsT38KQEzXQFAMeXlK95k+pvohRduxB4mFU6jqRy6aAL7cVkCtb1SmN8JpMz56Rpq ig2Qo3DAqzRcproDPMDFULmIvcbIKUcXcBfLU8A0= 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 , linux-block@vger.kernel.org, cgroups@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 19/20] block, bfq: fix overwrite of bfq_group pointer in bfq_find_set_group() Date: Sun, 15 Mar 2020 22:34:52 -0400 Message-Id: <20200316023453.1800-19-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200316023453.1800-1-sashal@kernel.org> References: <20200316023453.1800-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@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 9fe5952d117d5..ecd3d0ec2f3b6 100644 --- a/block/bfq-cgroup.c +++ b/block/bfq-cgroup.c @@ -525,12 +525,13 @@ 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