From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul E. McKenney" Subject: [PATCH tip/core/rcu 09/13] ipv6/sit: Apply rcu_access_pointer() to avoid sparse false positive Date: Tue, 24 Sep 2013 18:35:12 -0700 Message-ID: <1380072916-31557-9-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" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy , 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 ipip6_tunnel_unlink() 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: Alexey Kuznetsov Cc: James Morris Cc: Hideaki YOSHIFUJI Cc: Patrick McHardy Cc: netdev@vger.kernel.org --- net/ipv6/sit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index 7ee5cb9..fcb050a 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -157,7 +157,7 @@ static void ipip6_tunnel_unlink(struct sit_net *sitn, struct ip_tunnel *t) (iter = rtnl_dereference(*tp)) != NULL; tp = &iter->next) { if (t == iter) { - rcu_assign_pointer(*tp, t->next); + rcu_assign_pointer(*tp, rcu_access_pointer(t->next)); break; } } -- 1.8.1.5