Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932446Ab2KND61 (ORCPT ); Tue, 13 Nov 2012 22:58:27 -0500 Received: from smtp.outflux.net ([198.145.64.163]:38249 "EHLO smtp.outflux.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932268Ab2KND6Z (ORCPT ); Tue, 13 Nov 2012 22:58:25 -0500 Date: Tue, 13 Nov 2012 19:58:15 -0800 From: Kees Cook To: linux-kernel@vger.kernel.org Cc: James Morris , Kees Cook , John Johansen , "Serge E. Hallyn" , Eric Paris , linux-security-module@vger.kernel.org Subject: [PATCH] Yama: add RCU to drop read locking Message-ID: <20121114035815.GA29979@www.outflux.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-HELO: www.outflux.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3522 Lines: 118 Stop using spinlocks in the read path. Add RCU list to handle the readers. Signed-off-by: Kees Cook --- security/yama/yama_lsm.c | 43 ++++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 23 deletions(-) diff --git a/security/yama/yama_lsm.c b/security/yama/yama_lsm.c index b4c2984..17da6ca 100644 --- a/security/yama/yama_lsm.c +++ b/security/yama/yama_lsm.c @@ -30,6 +30,7 @@ struct ptrace_relation { struct task_struct *tracer; struct task_struct *tracee; struct list_head node; + struct rcu_head rcu; }; static LIST_HEAD(ptracer_relations); @@ -48,32 +49,29 @@ static DEFINE_SPINLOCK(ptracer_relations_lock); static int yama_ptracer_add(struct task_struct *tracer, struct task_struct *tracee) { - int rc = 0; - struct ptrace_relation *added; - struct ptrace_relation *entry, *relation = NULL; + struct ptrace_relation *relation, *added; added = kmalloc(sizeof(*added), GFP_KERNEL); if (!added) return -ENOMEM; + added->tracee = tracee; + added->tracer = tracer; + spin_lock_bh(&ptracer_relations_lock); - list_for_each_entry(entry, &ptracer_relations, node) - if (entry->tracee == tracee) { - relation = entry; - break; + list_for_each_entry_rcu(relation, &ptracer_relations, node) { + if (relation->tracee == tracee) { + list_replace_rcu(&relation->node, &added->node); + kfree_rcu(relation, rcu); + goto out; } - if (!relation) { - relation = added; - relation->tracee = tracee; - list_add(&relation->node, &ptracer_relations); } - relation->tracer = tracer; - spin_unlock_bh(&ptracer_relations_lock); - if (added != relation) - kfree(added); + list_add_rcu(&added->node, &ptracer_relations); - return rc; +out: + spin_unlock_bh(&ptracer_relations_lock); + return 0; } /** @@ -84,15 +82,16 @@ static int yama_ptracer_add(struct task_struct *tracer, static void yama_ptracer_del(struct task_struct *tracer, struct task_struct *tracee) { - struct ptrace_relation *relation, *safe; + struct ptrace_relation *relation; spin_lock_bh(&ptracer_relations_lock); - list_for_each_entry_safe(relation, safe, &ptracer_relations, node) + list_for_each_entry_rcu(relation, &ptracer_relations, node) { if (relation->tracee == tracee || (tracer && relation->tracer == tracer)) { - list_del(&relation->node); - kfree(relation); + list_del_rcu(&relation->node); + kfree_rcu(relation, rcu); } + } spin_unlock_bh(&ptracer_relations_lock); } @@ -217,11 +216,10 @@ static int ptracer_exception_found(struct task_struct *tracer, struct task_struct *parent = NULL; bool found = false; - spin_lock_bh(&ptracer_relations_lock); rcu_read_lock(); if (!thread_group_leader(tracee)) tracee = rcu_dereference(tracee->group_leader); - list_for_each_entry(relation, &ptracer_relations, node) + list_for_each_entry_rcu(relation, &ptracer_relations, node) if (relation->tracee == tracee) { parent = relation->tracer; found = true; @@ -231,7 +229,6 @@ static int ptracer_exception_found(struct task_struct *tracer, if (found && (parent == NULL || task_is_descendant(parent, tracer))) rc = 1; rcu_read_unlock(); - spin_unlock_bh(&ptracer_relations_lock); return rc; } -- 1.7.9.5 -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/