From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH tip/core/rcu 05/13] decnet: Apply rcu_access_pointer() to avoid sparse false positive Date: Tue, 24 Sep 2013 18:35:08 -0700 Message-ID: <1380072916-31557-5-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> 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" , "David S. Miller" , Thomas Graf , Gao feng , Stephen Hemminger , linux-decnet-user@lists.sourceforge.net, netdev@vger.kernel.org To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1380072916-31557-1-git-send-email-paulmck@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: 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 use in dn_insert_route() is legitimate: It 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: "David S. Miller" Cc: Thomas Graf Cc: Gao feng Cc: Stephen Hemminger Cc: linux-decnet-user@lists.sourceforge.net Cc: netdev@vger.kernel.org --- net/decnet/dn_route.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c index fe32388..3b1357b 100644 --- a/net/decnet/dn_route.c +++ b/net/decnet/dn_route.c @@ -345,7 +345,7 @@ static int dn_insert_route(struct dn_route *rt, unsigned int hash, struct dn_rou /* Put it first */ *rthp = rth->dst.dn_next; rcu_assign_pointer(rth->dst.dn_next, - dn_rt_hash_table[hash].chain); + rcu_access_pointer(dn_rt_hash_table[hash].chain)); rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth); dst_use(&rth->dst, now); @@ -358,7 +358,8 @@ static int dn_insert_route(struct dn_route *rt, unsigned int hash, struct dn_rou rthp = &rth->dst.dn_next; } - rcu_assign_pointer(rt->dst.dn_next, dn_rt_hash_table[hash].chain); + rcu_assign_pointer(rt->dst.dn_next, + rcu_access_pointer(dn_rt_hash_table[hash].chain)); rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt); dst_use(&rt->dst, now); -- 1.8.1.5