From patchwork Mon Feb 3 16:19:20 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 232101 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,URIBL_BLOCKED,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 1A7AEC35247 for ; Mon, 3 Feb 2020 16:46:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D826F2051A for ; Mon, 3 Feb 2020 16:46:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580748389; bh=/iqsiNq1ufmoQNtCN5R0k0FfUZr3NDO+99uNskwHkS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=X6o7GNW36DkcZRRnAadhrwTP4qxDs8Fne8S9qDw1urelH4BC5HMqJZ2xpXW6yX2g+ sJ8neNZmqaYujhbPvy/fv/ut4JkZ9wVlGSkD3sqp4os/qZaQW6ilNzt0L1eVCPqnXF vmHTW5MGDuhnrL5gXEFSN/CObkbnR5LAT488IVz4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729639AbgBCQ2m (ORCPT ); Mon, 3 Feb 2020 11:28:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:40354 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727257AbgBCQ2l (ORCPT ); Mon, 3 Feb 2020 11:28:41 -0500 Received: from localhost (unknown [104.132.45.99]) (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 37D2421744; Mon, 3 Feb 2020 16:28:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580747320; bh=/iqsiNq1ufmoQNtCN5R0k0FfUZr3NDO+99uNskwHkS8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qwiBlk9Z4QcnEq3xNdYVkuLdRj7Iuk300wIb9bbe4TGqGWL1m6IV00mRc1kBtP8fj /qnpgkf/tz4yIwsr25fmih4aTRAvqe1sT9UQMZEgZTb+OurdKvQXi9cgSbWuO8lv8V E73062Iu/WcU6JffXoUBosMdtyuOl0dUT1yRVzS0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Reinette Chatre , Xiaochen Shen , Borislav Petkov , Tony Luck , Thomas Gleixner , Sasha Levin Subject: [PATCH 4.14 35/89] x86/resctrl: Fix use-after-free due to inaccurate refcount of rdtgroup Date: Mon, 3 Feb 2020 16:19:20 +0000 Message-Id: <20200203161921.742470591@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200203161916.847439465@linuxfoundation.org> References: <20200203161916.847439465@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Xiaochen Shen commit 074fadee59ee7a9d2b216e9854bd4efb5dad679f upstream. There is a race condition in the following scenario which results in an use-after-free issue when reading a monitoring file and deleting the parent ctrl_mon group concurrently: Thread 1 calls atomic_inc() to take refcount of rdtgrp and then calls kernfs_break_active_protection() to drop the active reference of kernfs node in rdtgroup_kn_lock_live(). In Thread 2, kernfs_remove() is a blocking routine. It waits on all sub kernfs nodes to drop the active reference when removing all subtree kernfs nodes recursively. Thread 2 could block on kernfs_remove() until Thread 1 calls kernfs_break_active_protection(). Only after kernfs_remove() completes the refcount of rdtgrp could be trusted. Before Thread 1 calls atomic_inc() and kernfs_break_active_protection(), Thread 2 could call kfree() when the refcount of rdtgrp (sentry) is 0 instead of 1 due to the race. In Thread 1, in rdtgroup_kn_unlock(), referring to earlier rdtgrp memory (rdtgrp->waitcount) which was already freed in Thread 2 results in use-after-free issue. Thread 1 (rdtgroup_mondata_show) Thread 2 (rdtgroup_rmdir) -------------------------------- ------------------------- rdtgroup_kn_lock_live /* * kn active protection until * kernfs_break_active_protection(kn) */ rdtgrp = kernfs_to_rdtgroup(kn) rdtgroup_kn_lock_live atomic_inc(&rdtgrp->waitcount) mutex_lock rdtgroup_rmdir_ctrl free_all_child_rdtgrp /* * sentry->waitcount should be 1 * but is 0 now due to the race. */ kfree(sentry)*[1] /* * Only after kernfs_remove() * completes, the refcount of * rdtgrp could be trusted. */ atomic_inc(&rdtgrp->waitcount) /* kn->active-- */ kernfs_break_active_protection(kn) rdtgroup_ctrl_remove rdtgrp->flags = RDT_DELETED /* * Blocking routine, wait for * all sub kernfs nodes to drop * active reference in * kernfs_break_active_protection. */ kernfs_remove(rdtgrp->kn) rdtgroup_kn_unlock mutex_unlock atomic_dec_and_test( &rdtgrp->waitcount) && (flags & RDT_DELETED) kernfs_unbreak_active_protection(kn) kfree(rdtgrp) mutex_lock mon_event_read rdtgroup_kn_unlock mutex_unlock /* * Use-after-free: refer to earlier rdtgrp * memory which was freed in [1]. */ atomic_dec_and_test(&rdtgrp->waitcount) && (flags & RDT_DELETED) /* kn->active++ */ kernfs_unbreak_active_protection(kn) kfree(rdtgrp) Fix it by moving free_all_child_rdtgrp() to after kernfs_remove() in rdtgroup_rmdir_ctrl() to ensure it has the accurate refcount of rdtgrp. Backporting notes: Since upstream commit fa7d949337cc ("x86/resctrl: Rename and move rdt files to a separate directory"), the file arch/x86/kernel/cpu/intel_rdt_rdtgroup.c has been renamed and moved to arch/x86/kernel/cpu/resctrl/rdtgroup.c. Apply the change against file arch/x86/kernel/cpu/intel_rdt_rdtgroup.c for older stable trees. Upstream commit 17eafd076291 ("x86/intel_rdt: Split resource group removal in two") moved part of resource group removal code from rdtgroup_rmdir_mon() into a separate function rdtgroup_ctrl_remove(). Apply the change against original code base of rdtgroup_rmdir_mon() for older stable trees. Fixes: f3cbeacaa06e ("x86/intel_rdt/cqm: Add rmdir support") Suggested-by: Reinette Chatre Signed-off-by: Xiaochen Shen Signed-off-by: Borislav Petkov Reviewed-by: Reinette Chatre Reviewed-by: Tony Luck Acked-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1578500886-21771-3-git-send-email-xiaochen.shen@intel.com Signed-off-by: Sasha Levin --- arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c index 734996904dc3b..01574966d91fd 100644 --- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c +++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c @@ -1800,11 +1800,6 @@ static int rdtgroup_rmdir_ctrl(struct kernfs_node *kn, struct rdtgroup *rdtgrp, closid_free(rdtgrp->closid); free_rmid(rdtgrp->mon.rmid); - /* - * Free all the child monitor group rmids. - */ - free_all_child_rdtgrp(rdtgrp); - list_del(&rdtgrp->rdtgroup_list); /* @@ -1814,6 +1809,11 @@ static int rdtgroup_rmdir_ctrl(struct kernfs_node *kn, struct rdtgroup *rdtgrp, kernfs_get(kn); kernfs_remove(rdtgrp->kn); + /* + * Free all the child monitor group rmids. + */ + free_all_child_rdtgrp(rdtgrp); + return 0; }