From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756158Ab3IYBfh (ORCPT ); Tue, 24 Sep 2013 21:35:37 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:57191 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758390Ab3IYBf3 (ORCPT ); Tue, 24 Sep 2013 21:35:29 -0400 From: "Paul E. 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" , "John W. Linville" , Johannes Berg , "David S. Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH tip/core/rcu 10/13] mac80211: Apply rcu_access_pointer() to avoid sparse false positive Date: Tue, 24 Sep 2013 18:35:13 -0700 Message-Id: <1380072916-31557-10-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: 13092501-1344-0000-0000-000001EB03FA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@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 sta_info_hash_del() are legitimate: They is assigning a pointer to an element from an RCU-protected list, and all elements of this list are already visible to caller. This commit therefore silences this false positive by laundering the pointer using rcu_access_pointer() as suggested by Josh Triplett. Reported-by: kbuild test robot Signed-off-by: Paul E. McKenney Cc: "John W. Linville" Cc: Johannes Berg Cc: "David S. Miller" Cc: linux-wireless@vger.kernel.org Cc: netdev@vger.kernel.org --- net/mac80211/sta_info.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/mac80211/sta_info.c b/net/mac80211/sta_info.c index aeb967a..d18ab89 100644 --- a/net/mac80211/sta_info.c +++ b/net/mac80211/sta_info.c @@ -75,7 +75,7 @@ static int sta_info_hash_del(struct ieee80211_local *local, return -ENOENT; if (s == sta) { rcu_assign_pointer(local->sta_hash[STA_HASH(sta->sta.addr)], - s->hnext); + rcu_access_pointer(s->hnext)); return 0; } @@ -84,7 +84,7 @@ static int sta_info_hash_del(struct ieee80211_local *local, s = rcu_dereference_protected(s->hnext, lockdep_is_held(&local->sta_mtx)); if (rcu_access_pointer(s->hnext)) { - rcu_assign_pointer(s->hnext, sta->hnext); + rcu_assign_pointer(s->hnext, rcu_access_pointer(sta->hnext)); return 0; } -- 1.8.1.5