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 <edumazet@google.com>
Cc: Shawn Bohrer <sbohrer@rgmadvisors.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2e2aecb..16d246a 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1909,17 +1909,20 @@
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,