From e4c33317870e5f6f2af9cb4d07f4024a00f1a2ae Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Wed, 5 Feb 2025 15:51:10 +0000
Subject: [PATCH] ipv4: add RCU protection to ip4_dst_hoplimit()
[ Upstream commit 469308552ca4560176cfc100e7ca84add1bebd7c ]
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 <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250205155120.1676781-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 af8431b25f800..f396176022377 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -362,10 +362,15 @@ 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;
}
--
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