From 469308552ca4560176cfc100e7ca84add1bebd7c Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 5 Feb 2025 15:51:10 +0000 Subject: [PATCH] ipv4: add RCU protection to ip4_dst_hoplimit() ip4_dst_hoplimit() must use RCU protection to make sure the net structure it reads does not disappear. Fixes: fa50d974d104 ("ipv4: Namespaceify ip_default_ttl sysctl knob") Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20250205155120.1676781-3-edumazet@google.com Signed-off-by: Jakub Kicinski --- include/net/route.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/include/net/route.h b/include/net/route.h index f86775be3e29..c605fd5ec0c0 100644 --- a/include/net/route.h +++ b/include/net/route.h @@ -382,10 +382,15 @@ static inline int inet_iif(const struct sk_buff *skb) static inline int ip4_dst_hoplimit(const struct dst_entry *dst) { int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT); - struct net *net = dev_net(dst->dev); - if (hoplimit == 0) + if (hoplimit == 0) { + const struct net *net; + + rcu_read_lock(); + net = dev_net_rcu(dst->dev); hoplimit = READ_ONCE(net->ipv4.sysctl_ip_default_ttl); + rcu_read_unlock(); + } return hoplimit; }