From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: [PATCH] udp: fix a race in encap_rcv handling Date: Tue, 01 Nov 2011 23:56:59 +0100 Message-ID: <1320188219.4728.7.camel@edumazet-laptop> References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: netdev To: David Miller Return-path: Received: from mail-ww0-f44.google.com ([74.125.82.44]:50384 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754013Ab1KAW5F (ORCPT ); Tue, 1 Nov 2011 18:57:05 -0400 Received: by wwi36 with SMTP id 36so3807887wwi.1 for ; Tue, 01 Nov 2011 15:57:03 -0700 (PDT) In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: 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 --- net/ipv4/udp.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index ebaa96b..15b50df 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1397,6 +1397,8 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) 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 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb) */ /* 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,