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ipv4: use RCU protection in ipv4_default_advmss()

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ipv4_default_advmss() must use RCU protection to make
sure the net structure it reads does not disappear.

Fixes: 2e9589ff80 ("ipv4: Namespaceify min_adv_mss sysctl knob")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250205155120.1676781-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2025-02-05 15:51:12 +00:00 • committed by Jakub Kicinski
parent 071d801286
commit 71b8471c93
1 changed files with 8 additions and 3 deletions
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11
net/ipv4/route.c
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@ -1307,10 +1307,15 @@ static void set_class_tag(struct rtable *rt, u32 tag)
static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
{
struct net *net = dev_net(dst->dev);
unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
unsigned int advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
net->ipv4.ip_rt_min_advmss);
unsigned int advmss;
struct net *net;
rcu_read_lock();
net = dev_net_rcu(dst->dev);
advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
net->ipv4.ip_rt_min_advmss);
rcu_read_unlock();
return min(advmss, IPV4_MAX_PMTU - header_size);
}