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ipv4: use RCU protection in __ip_rt_update_pmtu()

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

Fixes: 2fbc6e89b2 ("ipv4: Update exception handling for multipath routes via same device")
Fixes: 1de6b15a43 ("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>
This commit is contained in:
Eric Dumazet 2025-02-05 15:51:15 +00:00 • committed by Jakub Kicinski
parent 719817cd29
commit 139512191b
1 changed files with 6 additions and 5 deletions
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11
net/ipv4/route.c
View file

@ -1008,9 +1008,9 @@ 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))
@ -1020,6 +1020,8 @@ 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);
@ -1027,9 +1029,8 @@ 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;
@ -1043,14 +1044,14 @@ 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();
}