From 35bcb7202d57640fa3d20b4dda865a88147ae180 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 5 Feb 2025 15:51:18 +0000
Subject: [PATCH] ipv6: use RCU protection in ip6_default_advmss()
[ Upstream commit 3c8ffcd248da34fc41e52a46e51505900115fc2a ]
ip6_default_advmss() needs rcu protection to make
sure the net structure it reads does not disappear.
Fixes: 5578689a4e3c ("[NETNS][IPV6] route6 - make route6 per namespace")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250205155120.1676781-11-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/route.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index f3268bac9f198..17918f411386a 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3190,13 +3190,18 @@ static unsigned int ip6_default_advmss(const struct dst_entry *dst)
{
struct net_device *dev = dst->dev;
unsigned int mtu = dst_mtu(dst);
- struct net *net = dev_net(dev);
+ struct net *net;
mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);
+ rcu_read_lock();
+
+ net = dev_net_rcu(dev);
if (mtu < net->ipv6.sysctl.ip6_rt_min_advmss)
mtu = net->ipv6.sysctl.ip6_rt_min_advmss;
+ rcu_read_unlock();
+
/*
* Maximal non-jumbo IPv6 payload is IPV6_MAXPLEN and
* corresponding MSS is IPV6_MAXPLEN - tcp_header_size.
--
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