From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760332AbYDVAeZ (ORCPT ); Mon, 21 Apr 2008 20:34:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751958AbYDVAeR (ORCPT ); Mon, 21 Apr 2008 20:34:17 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:36892 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751853AbYDVAeQ (ORCPT ); Mon, 21 Apr 2008 20:34:16 -0400 Date: Mon, 21 Apr 2008 17:34:12 -0700 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, akpm@linux-foundation.org, rostedt@goodmis.org, dwalker@mvista.com, sdietrich@novell.com, dvhltc@us.ibm.com, niv@us.ibm.com Subject: [PATCH] SELinux fixups needed for preemptable RCU from -rt Message-ID: <20080422003412.GA9983@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! The attached patch needs to move from -rt to mainline given preemptable RCU. This patch fixes SELinux code that implicitly assumes that disabling preemption prevents an RCU grace period from completing, an assumption that is valid for Classic RCU, but not necessarily for preemptable RCU. Explicit rcu_read_lock() calls are thus added. Pointed-out-by: Paul E. McKenney --- security/selinux/avc.c | 9 +++++++++ security/selinux/netif.c | 2 ++ 2 files changed, 11 insertions(+) Index: linux-2.6.24.4-rt4/security/selinux/avc.c =================================================================== --- linux-2.6.24.4-rt4.orig/security/selinux/avc.c 2008-03-24 19:05:09.000000000 -0400 +++ linux-2.6.24.4-rt4/security/selinux/avc.c 2008-03-24 19:06:41.000000000 -0400 @@ -312,6 +312,7 @@ static inline int avc_reclaim_node(void) if (!spin_trylock_irqsave(&avc_cache.slots_lock[hvalue], flags)) continue; + rcu_read_lock(); list_for_each_entry(node, &avc_cache.slots[hvalue], list) { if (atomic_dec_and_test(&node->ae.used)) { /* Recently Unused */ @@ -319,11 +320,13 @@ static inline int avc_reclaim_node(void) avc_cache_stats_incr(reclaims); ecx++; if (ecx >= AVC_CACHE_RECLAIM) { + rcu_read_unlock(); spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags); goto out; } } } + rcu_read_unlock(); spin_unlock_irqrestore(&avc_cache.slots_lock[hvalue], flags); } out: @@ -807,8 +810,14 @@ int avc_ss_reset(u32 seqno) for (i = 0; i < AVC_CACHE_SLOTS; i++) { spin_lock_irqsave(&avc_cache.slots_lock[i], flag); + /* + * On -rt the outer spinlock does not prevent RCU + * from being performed: + */ + rcu_read_lock(); list_for_each_entry(node, &avc_cache.slots[i], list) avc_node_delete(node); + rcu_read_unlock(); spin_unlock_irqrestore(&avc_cache.slots_lock[i], flag); } Index: linux-2.6.24.4-rt4/security/selinux/netif.c =================================================================== --- linux-2.6.24.4-rt4.orig/security/selinux/netif.c 2008-03-24 19:05:09.000000000 -0400 +++ linux-2.6.24.4-rt4/security/selinux/netif.c 2008-03-24 19:06:41.000000000 -0400 @@ -210,6 +210,7 @@ static void sel_netif_flush(void) { int idx; + rcu_read_lock(); spin_lock_bh(&sel_netif_lock); for (idx = 0; idx < SEL_NETIF_HASH_SIZE; idx++) { struct sel_netif *netif; @@ -218,6 +219,7 @@ static void sel_netif_flush(void) sel_netif_destroy(netif); } spin_unlock_bh(&sel_netif_lock); + rcu_read_unlock(); } static int sel_netif_avc_callback(u32 event, u32 ssid, u32 tsid,