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Date: Sat, 23 Feb 2019 01:34:29 -0500
From: "Joel Fernandes (Google)" <joel@...lfernandes.org>
To: linux-kernel@...r.kernel.org
Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>,
	Alexei Starovoitov <ast@...nel.org>,
	Christian Brauner <christian@...uner.io>,
	Daniel Borkmann <daniel@...earbox.net>,
	David Ahern <dsahern@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...hat.com>,
	Jakub Kicinski <jakub.kicinski@...ronome.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Josh Triplett <josh@...htriplett.org>,
	keescook@...omium.org,
	kernel-hardening@...ts.openwall.com,
	kernel-team@...roid.com,
	Kirill Tkhai <ktkhai@...tuozzo.com>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Martin KaFai Lau <kafai@...com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	netdev@...r.kernel.org,
	"Paul E. McKenney" <paulmck@...ux.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Quentin Perret <quentin.perret@....com>,
	rcu@...r.kernel.org,
	Song Liu <songliubraving@...com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	xdp-newbies@...r.kernel.org,
	Yonghong Song <yhs@...com>
Subject: [PATCH v2 1/6] net: rtnetlink: Fix incorrect RCU API usage

rtnl_register_internal() and rtnl_unregister_all tries to directly
dereference an RCU protected pointed outside RCU read side section.
While this is Ok to do since a lock is held, let us use the correct
API to avoid programmer bugs in the future.

This also fixes sparse warnings arising from not using RCU API.

net/core/rtnetlink.c:332:13: warning: incorrect type in assignment
(different address spaces) net/core/rtnetlink.c:332:13:    expected
struct rtnl_link **tab net/core/rtnetlink.c:332:13:    got struct
rtnl_link *[noderef] <asn:4>*<noident>

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 net/core/rtnetlink.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 5ea1bed08ede..98be4b4818a9 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -188,7 +188,7 @@ static int rtnl_register_internal(struct module *owner,
 	msgindex = rtm_msgindex(msgtype);
 
 	rtnl_lock();
-	tab = rtnl_msg_handlers[protocol];
+	tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
 	if (tab == NULL) {
 		tab = kcalloc(RTM_NR_MSGTYPES, sizeof(void *), GFP_KERNEL);
 		if (!tab)
@@ -329,7 +329,7 @@ void rtnl_unregister_all(int protocol)
 	BUG_ON(protocol < 0 || protocol > RTNL_FAMILY_MAX);
 
 	rtnl_lock();
-	tab = rtnl_msg_handlers[protocol];
+	tab = rtnl_dereference(rtnl_msg_handlers[protocol]);
 	if (!tab) {
 		rtnl_unlock();
 		return;
-- 
2.21.0.rc0.258.g878e2cd30e-goog

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