From patchwork Wed Sep 25 01:35:15 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Paul E. McKenney" X-Patchwork-Id: 277657 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 653142C009D for ; Wed, 25 Sep 2013 11:36:52 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932749Ab3IYBfb (ORCPT ); Tue, 24 Sep 2013 21:35:31 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:35094 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758388Ab3IYBf3 (ORCPT ); Tue, 24 Sep 2013 21:35:29 -0400 Received: from /spool/local by e32.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, "Paul E. McKenney" , Stephen Hemminger , "David S. Miller" , bridge@lists.linux-foundation.org, netdev@vger.kernel.org Subject: [PATCH tip/core/rcu 12/13] bonding/bond_main: Apply rcu_access_pointer() to avoid sparse false positive Date: Tue, 24 Sep 2013 18:35:15 -0700 Message-Id: <1380072916-31557-12-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1380072916-31557-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20130925013451.GA31260@linux.vnet.ibm.com> <1380072916-31557-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13092501-0928-0000-0000-000001FEE9FA Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: "Paul E. McKenney" The sparse checking for rcu_assign_pointer() was recently upgraded to reject non-__kernel address spaces. This also rejects __rcu, which is almost always the right thing to do. However, the uses in bond_change_active_slave(), bond_enslave(), and __bond_release_one() are legitimate: They are assigning a pointer to an element from an RCU-protected list (or a NULL pointer), and all elements of this list are already visible to caller. This commit therefore silences these false positives either by laundering the pointers using rcu_access_pointer() as suggested by Josh Triplett, or by using RCU_INIT_POINTER() for NULL pointer assignments. Reported-by: kbuild test robot Signed-off-by: Paul E. McKenney Cc: Stephen Hemminger Cc: "David S. Miller" Cc: bridge@lists.linux-foundation.org Cc: netdev@vger.kernel.org --- drivers/net/bonding/bond_main.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 72df399..2f276b9 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -890,7 +890,8 @@ void bond_change_active_slave(struct bonding *bond, struct slave *new_active) if (new_active) bond_set_slave_active_flags(new_active); } else { - rcu_assign_pointer(bond->curr_active_slave, new_active); + rcu_assign_pointer(bond->curr_active_slave, + rcu_access_pointer(new_active)); } if (bond->params.mode == BOND_MODE_ACTIVEBACKUP) { @@ -1601,7 +1602,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev) * so we can change it without calling change_active_interface() */ if (!bond->curr_active_slave && new_slave->link == BOND_LINK_UP) - rcu_assign_pointer(bond->curr_active_slave, new_slave); + rcu_assign_pointer(bond->curr_active_slave, + rcu_access_pointer(new_slave)); break; } /* switch(bond_mode) */ @@ -1801,7 +1803,7 @@ static int __bond_release_one(struct net_device *bond_dev, } if (all) { - rcu_assign_pointer(bond->curr_active_slave, NULL); + RCU_INIT_POINTER(bond->curr_active_slave, NULL); } else if (oldcurrent == slave) { /* * Note that we hold RTNL over this sequence, so there