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ipv6: use RCU protection in ip6_default_advmss()

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ip6_default_advmss() needs rcu protection to make
sure the net structure it reads does not disappear.

Fixes: 5578689a4e ("[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>
This commit is contained in:
Eric Dumazet 2025-02-05 15:51:18 +00:00 • committed by Jakub Kicinski
parent afec62cd0a
commit 3c8ffcd248
1 changed files with 6 additions and 1 deletions
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7
net/ipv6/route.c
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@ -3196,13 +3196,18 @@ 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.