From c48c1a4ca79df7e6901aef703cb5ca11bfad38e6 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 5 Feb 2025 15:51:15 +0000
Subject: [PATCH] ipv4: use RCU protection in __ip_rt_update_pmtu()
[ Upstream commit 139512191bd06f1b496117c76372b2ce372c9a41 ]
__ip_rt_update_pmtu() must use RCU protection to make
sure the net structure it reads does not disappear.
Fixes: 2fbc6e89b2f1 ("ipv4: Update exception handling for multipath routes via same device")
Fixes: 1de6b15a434c ("Namespaceify min_pmtu sysctl")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250205155120.1676781-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/route.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 0bda6916ebcfb..4574dcba9f193 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1020,9 +1020,9 @@ out: kfree_skb_reason(skb, reason);
static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
{
struct dst_entry *dst = &rt->dst;
- struct net *net = dev_net(dst->dev);
struct fib_result res;
bool lock = false;
+ struct net *net;
u32 old_mtu;
if (ip_mtu_locked(dst))
@@ -1032,6 +1032,8 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
if (old_mtu < mtu)
return;
+ rcu_read_lock();
+ net = dev_net_rcu(dst->dev);
if (mtu < net->ipv4.ip_rt_min_pmtu) {
lock = true;
mtu = min(old_mtu, net->ipv4.ip_rt_min_pmtu);
@@ -1039,9 +1041,8 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
if (rt->rt_pmtu == mtu && !lock &&
time_before(jiffies, dst->expires - net->ipv4.ip_rt_mtu_expires / 2))
- return;
+ goto out;
- rcu_read_lock();
if (fib_lookup(net, fl4, &res, 0) == 0) {
struct fib_nh_common *nhc;
@@ -1055,14 +1056,14 @@ static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
update_or_create_fnhe(nhc, fl4->daddr, 0, mtu, lock,
jiffies + net->ipv4.ip_rt_mtu_expires);
}
- rcu_read_unlock();
- return;
+ goto out;
}
#endif /* CONFIG_IP_ROUTE_MULTIPATH */
nhc = FIB_RES_NHC(res);
update_or_create_fnhe(nhc, fl4->daddr, 0, mtu, lock,
jiffies + net->ipv4.ip_rt_mtu_expires);
}
+out:
rcu_read_unlock();
}
--
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