From 7add7a11fdc550f96d35dc3306d8c0e6f3d7a3bb Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 7 Feb 2025 13:58:39 +0000
Subject: [PATCH] ndisc: extend RCU protection in ndisc_send_skb()
[ Upstream commit ed6ae1f325d3c43966ec1b62ac1459e2b8e45640 ]
ndisc_send_skb() can be called without RTNL or RCU held.
Acquire rcu_read_lock() earlier, so that we can use dev_net_rcu()
and avoid a potential UAF.
Fixes: 1762f7e88eb3 ("[NETNS][IPV6] ndisc - make socket control per namespace")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250207135841.1948589-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv6/ndisc.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 2e8e0847631e3..1a6408a24d21c 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -471,16 +471,20 @@ static void ip6_nd_hdr(struct sk_buff *skb,
void ndisc_send_skb(struct sk_buff *skb, const struct in6_addr *daddr,
const struct in6_addr *saddr)
{
+ struct icmp6hdr *icmp6h = icmp6_hdr(skb);
struct dst_entry *dst = skb_dst(skb);
- struct net *net = dev_net(skb->dev);
- struct sock *sk = net->ipv6.ndisc_sk;
struct inet6_dev *idev;
+ struct net *net;
+ struct sock *sk;
int err;
- struct icmp6hdr *icmp6h = icmp6_hdr(skb);
u8 type;
type = icmp6h->icmp6_type;
+ rcu_read_lock();
+
+ net = dev_net_rcu(skb->dev);
+ sk = net->ipv6.ndisc_sk;
if (!dst) {
struct flowi6 fl6;
int oif = skb->dev->ifindex;
@@ -488,6 +492,7 @@ void ndisc_send_skb(struct sk_buff *skb, const struct in6_addr *daddr,
icmpv6_flow_init(sk, &fl6, type, saddr, daddr, oif);
dst = icmp6_dst_alloc(skb->dev, &fl6);
if (IS_ERR(dst)) {
+ rcu_read_unlock();
kfree_skb(skb);
return;
}
@@ -502,7 +507,6 @@ void ndisc_send_skb(struct sk_buff *skb, const struct in6_addr *daddr,
ip6_nd_hdr(skb, saddr, daddr, inet6_sk(sk)->hop_limit, skb->len);
- rcu_read_lock();
idev = __in6_dev_get(dst->dev);
IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, skb->len);
--
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