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ndisc: extend RCU protection in ndisc_send_skb()

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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: 1762f7e88e ("[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>
This commit is contained in:
Eric Dumazet 2025-02-07 13:58:39 +00:00 • committed by Jakub Kicinski
parent 6d0ce46a93
commit ed6ae1f325
1 changed files with 10 additions and 6 deletions
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16
net/ipv6/ndisc.c
View file

@ -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 dst_entry *dst = skb_dst(skb);
struct net *net = dev_net(skb->dev);
struct sock *sk = net->ipv6.ndisc_sk;
struct inet6_dev *idev;
int err;
struct icmp6hdr *icmp6h = icmp6_hdr(skb);
struct dst_entry *dst = skb_dst(skb);
struct inet6_dev *idev;
struct net *net;
struct sock *sk;
int err;
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, READ_ONCE(inet6_sk(sk)->hop_limit), skb->len);
rcu_read_lock();
idev = __in6_dev_get(dst->dev);
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTREQUESTS);