ipv6: tcp: fix race in IPV6_2292PKTOPTIONS
IPv6 TCP sockets store in np->pktoptions skbs, and use skb_set_owner_r()
to charge the skb to socket.
It means that destructor must be called while socket is locked.
Therefore, we cannot use skb_get() or atomic_inc(&skb->users)
to protect ourselves : kfree_skb() might race with other users
manipulating sk->sk_forward_alloc
Fix this race by holding socket lock for the duration of
ip6_datagram_recv_ctl()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 66980d8..8d766d9 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -996,13 +996,9 @@
lock_sock(sk);
skb = np->pktoptions;
if (skb)
- atomic_inc(&skb->users);
- release_sock(sk);
-
- if (skb) {
ip6_datagram_recv_ctl(sk, &msg, skb);
- kfree_skb(skb);
- } else {
+ release_sock(sk);
+ if (!skb) {
if (np->rxopt.bits.rxinfo) {
struct in6_pktinfo src_info;
src_info.ipi6_ifindex = np->mcast_oif ? np->mcast_oif :