From 610438b74496b2986a9025f8e23c134cb638e338 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 11 Dec 2013 08:10:05 -0800 Subject: [PATCH] udp: ipv4: fix potential use after free in udp_v4_early_demux() 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 Cc: Shawn Bohrer Signed-off-by: David S. Miller --- net/ipv4/udp.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) 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, -- 2.20.1