Commit 610438b7 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

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: 421b3885 ("udp: ipv4: Add udp early demux")
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ce232ce0
......@@ -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,
......
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