6.12-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ 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 f707cdb26ff20..41b320f0c20eb 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -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(); }