From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 31 Aug 2016 17:54:09 +0200
Subject: net: add a lock around icmp_sk()
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 112ab82c78f6224e15d7e09baae9e16349bceb08
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

It looks like the this_cpu_ptr() access in icmp_sk() is protected with
local_bh_disable(). To avoid missing serialization in -RT I am adding
here a local lock. No crash has been observed, this is just precaution.

Cc: stable-rt@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 net/ipv4/icmp.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -77,6 +77,7 @@
 #include <linux/string.h>
 #include <linux/netfilter_ipv4.h>
 #include <linux/slab.h>
+#include <linux/locallock.h>
 #include <net/snmp.h>
 #include <net/ip.h>
 #include <net/route.h>
@@ -204,6 +205,8 @@ static const struct icmp_control icmp_po
  *
  *	On SMP we have one ICMP socket per-cpu.
  */
+static DEFINE_LOCAL_IRQ_LOCK(icmp_sk_lock);
+
 static struct sock *icmp_sk(struct net *net)
 {
 	return *this_cpu_ptr(net->ipv4.icmp_sk);
@@ -417,6 +420,7 @@ static void icmp_reply(struct icmp_bxm *
 
 	/* Needed by both icmp_global_allow and icmp_xmit_lock */
 	local_bh_disable();
+	local_lock(icmp_sk_lock);
 
 	/* global icmp_msgs_per_sec */
 	if (!icmpv4_global_allow(net, type, code))
@@ -461,6 +465,7 @@ static void icmp_reply(struct icmp_bxm *
 out_unlock:
 	icmp_xmit_unlock(sk);
 out_bh_enable:
+	local_unlock(icmp_sk_lock);
 	local_bh_enable();
 }
 
@@ -656,6 +661,7 @@ void icmp_send(struct sk_buff *skb_in, i
 
 	/* Needed by both icmp_global_allow and icmp_xmit_lock */
 	local_bh_disable();
+	local_lock(icmp_sk_lock);
 
 	/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
 	 * incoming dev is loopback.  If outgoing dev change to not be
@@ -744,6 +750,7 @@ void icmp_send(struct sk_buff *skb_in, i
 out_unlock:
 	icmp_xmit_unlock(sk);
 out_bh_enable:
+	local_unlock(icmp_sk_lock);
 	local_bh_enable();
 out:;
 }