udp: fix a race in encap_rcv handling
udp_queue_rcv_skb() has a possible race in encap_rcv handling, since
this pointer can be changed anytime.
We should use ACCESS_ONCE() to close the race.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 131d8a7..ab0966d 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1397,6 +1397,8 @@
nf_reset(skb);
if (up->encap_type) {
+ int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
+
/*
* This is an encapsulation socket so pass the skb to
* the socket's udp_encap_rcv() hook. Otherwise, just
@@ -1409,11 +1411,11 @@
*/
/* if we're overly short, let UDP handle it */
- if (skb->len > sizeof(struct udphdr) &&
- up->encap_rcv != NULL) {
+ encap_rcv = ACCESS_ONCE(up->encap_rcv);
+ if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
int ret;
- ret = (*up->encap_rcv)(sk, skb);
+ ret = encap_rcv(sk, skb);
if (ret <= 0) {
UDP_INC_STATS_BH(sock_net(sk),
UDP_MIB_INDATAGRAMS,