udp: fix possible user after free in error handler

Similar to the previous commit, this addresses the same issue for
ipv4: use a single fetch operation and use the correct rcu
annotation.

Fixes: e7cc082455cb ("udp: Support for error handlers of tunnels with arbitrary destination port")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Stefano Brivio <sbrivio@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 5c3cd5d..372fdc5 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -562,10 +562,12 @@ static int __udp4_lib_err_encap_no_sk(struct sk_buff *skb, u32 info)
 
        for (i = 0; i < MAX_IPTUN_ENCAP_OPS; i++) {
                int (*handler)(struct sk_buff *skb, u32 info);
+               const struct ip_tunnel_encap_ops *encap;
 
-               if (!iptun_encaps[i])
+               encap = rcu_dereference(iptun_encaps[i]);
+               if (!encap)
                        continue;
-               handler = rcu_dereference(iptun_encaps[i]->err_handler);
+               handler = encap->err_handler;
                if (handler && !handler(skb, info))
                        return 0;
        }