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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 17D7AC433DF for ; Mon, 17 Aug 2020 00:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EB58A2075D for ; Mon, 17 Aug 2020 00:45:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726697AbgHQAp1 (ORCPT ); Sun, 16 Aug 2020 20:45:27 -0400 Received: from mx2.suse.de ([195.135.220.15]:54704 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726451AbgHQApZ (ORCPT ); Sun, 16 Aug 2020 20:45:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 24924AC23; Mon, 17 Aug 2020 00:45:49 +0000 (UTC) From: Davidlohr Bueso To: akpm@linux-foundation.org Cc: oleg@redhat.com, axboe@kernel.dk, linux-kernel@vger.kernel.org, Davidlohr Bueso , Greg Thelen , Davidlohr Bueso Subject: [PATCH 2/2] block: fix ioprio_get/set(IOPRIO_WHO_PGRP) vs setuid(2) Date: Sun, 16 Aug 2020 17:31:48 -0700 Message-Id: <20200817003148.23691-3-dave@stgolabs.net> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200817003148.23691-1-dave@stgolabs.net> References: <20200817003148.23691-1-dave@stgolabs.net> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org do_each_pid_thread(PIDTYPE_PGID) can race with a concurrent change_pid(PIDTYPE_PGID) that can move the task from one hlist to another while iterating. Serialize ioprio_get/set to take the tasklist_lock in this case. Fixes: d69b78ba1de (ioprio: grab rcu_read_lock in sys_ioprio_{set,get}()) Cc: Greg Thelen Signed-off-by: Davidlohr Bueso --- block/ioprio.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/block/ioprio.c b/block/ioprio.c index 77bcab11dce5..4ede2da961bb 100644 --- a/block/ioprio.c +++ b/block/ioprio.c @@ -119,11 +119,13 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio) pgrp = task_pgrp(current); else pgrp = find_vpid(who); + read_lock(&tasklist_lock); do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { ret = set_task_ioprio(p, ioprio); if (ret) break; } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + read_unlock(&tasklist_lock); break; case IOPRIO_WHO_USER: uid = make_kuid(current_user_ns(), who); @@ -207,6 +209,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) pgrp = task_pgrp(current); else pgrp = find_vpid(who); + read_lock(&tasklist_lock); do_each_pid_thread(pgrp, PIDTYPE_PGID, p) { tmpio = get_task_ioprio(p); if (tmpio < 0) @@ -216,6 +219,7 @@ SYSCALL_DEFINE2(ioprio_get, int, which, int, who) else ret = ioprio_best(ret, tmpio); } while_each_pid_thread(pgrp, PIDTYPE_PGID, p); + read_unlock(&tasklist_lock); break; case IOPRIO_WHO_USER: uid = make_kuid(current_user_ns(), who); -- 2.26.2