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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>
This commit is contained in:
Eric Dumazet 2011-11-01 12:56:59 +00:00 committed by David S. Miller
parent 501e89d3ae
commit 0ad92ad03a
1 changed files with 5 additions and 3 deletions
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8
net/ipv4/udp.c
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@ -1397,6 +1397,8 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
nf_reset(skb); nf_reset(skb);
if (up->encap_type) { if (up->encap_type) {
int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
/* /*
* This is an encapsulation socket so pass the skb to * This is an encapsulation socket so pass the skb to
* the socket's udp_encap_rcv() hook. Otherwise, just * the socket's udp_encap_rcv() hook. Otherwise, just
@ -1409,11 +1411,11 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
*/ */
/* if we're overly short, let UDP handle it */ /* if we're overly short, let UDP handle it */
if (skb->len > sizeof(struct udphdr) && encap_rcv = ACCESS_ONCE(up->encap_rcv);
up->encap_rcv != NULL) { if (skb->len > sizeof(struct udphdr) && encap_rcv != NULL) {
int ret; int ret;
ret = (*up->encap_rcv)(sk, skb); ret = encap_rcv(sk, skb);
if (ret <= 0) { if (ret <= 0) {
UDP_INC_STATS_BH(sock_net(sk), UDP_INC_STATS_BH(sock_net(sk),
UDP_MIB_INDATAGRAMS, UDP_MIB_INDATAGRAMS,