From c9eb57127331f638a03b5426fa129c2078c9304e Mon Sep 17 00:00:00 2001
Message-Id: <c9eb57127331f638a03b5426fa129c2078c9304e.1599166691.git.zanussi@kernel.org>
In-Reply-To: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
References: <56457dc415803c8abc5acb513ada877a79596f05.1599166690.git.zanussi@kernel.org>
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 31 Aug 2016 17:54:09 +0200
Subject: [PATCH 203/333] net: add a lock around icmp_sk()
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.142-rt63.tar.xz

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>
---
 net/ipv4/icmp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 4efa5e33513e..de67d595e298 100644
--- 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_pointers[NR_ICMP_TYPES+1];
  *
  *	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);
@@ -214,12 +217,16 @@ static inline struct sock *icmp_xmit_lock(struct net *net)
 {
 	struct sock *sk;
 
+	if (!local_trylock(icmp_sk_lock))
+		return NULL;
+
 	sk = icmp_sk(net);
 
 	if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
 		/* This can happen if the output path signals a
 		 * dst_link_failure() for an outgoing ICMP packet.
 		 */
+		local_unlock(icmp_sk_lock);
 		return NULL;
 	}
 	return sk;
@@ -228,6 +235,7 @@ static inline struct sock *icmp_xmit_lock(struct net *net)
 static inline void icmp_xmit_unlock(struct sock *sk)
 {
 	spin_unlock(&sk->sk_lock.slock);
+	local_unlock(icmp_sk_lock);
 }
 
 int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
-- 
2.17.1

