diff mbox

udp: ipv4: fix potential use after free in udp_v4_early_demux()

Message ID 1386778205.30495.374.camel@edumazet-glaptop2.roam.corp.google.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Eric Dumazet Dec. 11, 2013, 4:10 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

pskb_may_pull() can reallocate skb->head, we need to move the
initialization of iph and uh pointers after its call.

Fixes: 421b3885bf6d ("udp: ipv4: Add udp early demux")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>
---
 net/ipv4/udp.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)



--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Comments

David Miller Dec. 11, 2013, 9:16 p.m. UTC | #1 
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 11 Dec 2013 08:10:05 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> pskb_may_pull() can reallocate skb->head, we need to move the
> initialization of iph and uh pointers after its call.
> 
> Fixes: 421b3885bf6d ("udp: ipv4: Add udp early demux")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>

Applied, thanks Eric.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2e2aecbe22c4..16d246a51a02 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1909,17 +1909,20 @@  static struct sock *__udp4_lib_demux_lookup(struct net *net,
 
 void udp_v4_early_demux(struct sk_buff *skb)
 {
-	const struct iphdr *iph = ip_hdr(skb);
-	const struct udphdr *uh = udp_hdr(skb);
+	struct net *net = dev_net(skb->dev);
+	const struct iphdr *iph;
+	const struct udphdr *uh;
 	struct sock *sk;
 	struct dst_entry *dst;
-	struct net *net = dev_net(skb->dev);
 	int dif = skb->dev->ifindex;
 
 	/* validate the packet */
 	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct udphdr)))
 		return;
 
+	iph = ip_hdr(skb);
+	uh = udp_hdr(skb);
+
 	if (skb->pkt_type == PACKET_BROADCAST ||
 	    skb->pkt_type == PACKET_MULTICAST)
 		sk = __udp4_lib_mcast_demux_lookup(net, uh->dest, iph->daddr,