5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ 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 92e35b3096dba..fe10f1ce167be 100644 --- a/net/ipv6/ndisc.c +++ b/net/ipv6/ndisc.c @@ -470,16 +470,20 @@ static 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; @@ -487,6 +491,7 @@ static void ndisc_send_skb(struct sk_buff *skb, 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; } @@ -501,7 +506,6 @@ static void ndisc_send_skb(struct sk_buff *skb,
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);