diff --git a/include/net/ip.h b/include/net/ip.h
index 6b87c7ef645904225d9e80d3fe9c996c23c99d71..b97886996d798b42980fbab3588320dda4ca0541 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -443,7 +443,7 @@ static inline unsigned int ip_dst_mtu_maybe_forward(const struct dst_entry *dst,
 	struct net *net = dev_net(dst->dev);
 	unsigned int mtu;
 
-	if (net->ipv4.sysctl_ip_fwd_use_pmtu ||
+	if (READ_ONCE(net->ipv4.sysctl_ip_fwd_use_pmtu) ||
 	    ip_mtu_locked(dst) ||
 	    !forwarding)
 		return dst_mtu(dst);
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 9bd3cd2177f4824cb46fdf1a8ee9db214343719e..216f76b548ff5eb4659ad715c45cc7b9b7b4dd59 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1442,7 +1442,7 @@ u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr)
 	struct fib_info *fi = res->fi;
 	u32 mtu = 0;
 
-	if (dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu ||
+	if (READ_ONCE(dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu) ||
 	    fi->fib_metrics->metrics[RTAX_LOCK - 1] & (1 << RTAX_MTU))
 		mtu = fi->fib_mtu;