udp: Fix a memory leak in udp_read_sock()

sk_psock_verdict_recv() clones the skb and uses the clone
afterward, so udp_read_sock() should free the skb after using
it, regardless of error or not.

This fixes a real kmemleak.

Fixes: d7f571188ecf ("udp: Implement ->read_sock() for sockmap")
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20210615021342.7416-4-xiyou.wangcong@gmail.com

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1307ad0..8091276 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1798,11 +1798,13 @@ int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
                if (used <= 0) {
                        if (!copied)
                                copied = used;
+                       kfree_skb(skb);
                        break;
                } else if (used <= skb->len) {
                        copied += used;
                }
 
+               kfree_skb(skb);
                if (!desc->count)
                        break;
        }