This is a note to let you know that I've just added the patch titled
ipv4: use RCU protection in ipv4_default_advmss()
to the 6.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ipv4-use-rcu-protection-in-ipv4_default_advmss.patch
and it can be found in the queue-6.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b949ea11155f9806574e4f0502e164d073d585f6
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Wed Feb 5 15:51:12 2025 +0000
ipv4: use RCU protection in ipv4_default_advmss()
[ Upstream commit 71b8471c93fa0bcab911fcb65da1eb6c4f5f735f ]
ipv4_default_advmss() must use RCU protection to make
sure the net structure it reads does not disappear.
Fixes: 2e9589ff809e ("ipv4: Namespaceify min_adv_mss sysctl knob")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Reviewed-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Link: https://patch.msgid.link/20250205155120.1676781-5-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 3a1467f2d553f..829c8d41aaae2 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -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);
}
