6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet <edumazet@xxxxxxxxxx>
[ 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>
---
net/ipv4/route.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 61fc2166a870e..15cf2949ce951 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1306,10 +1306,15 @@ 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);
}
--
2.39.5
