udp: Validate checksum in udp_read_sock()

BugLink: https://bugs.launchpad.net/bugs/1952579
[ Upstream commit 099f896f498a2b26d84f4ddae039b2c542c18b48 ]

It turns out the skb's in sock receive queue could have bad checksums, as
both ->poll() and ->recvmsg() validate checksums. We have to do the same
for ->read_sock() path too before they are redirected in sockmap.

Fixes: d7f571188ecf ("udp: Implement ->read_sock() for sockmap")
Reported-by: Daniel Borkmann <daniel@iogearbox.net>
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>
Link: https://lore.kernel.org/bpf/20211115044006.26068-1-xiyou.wangcong@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2fffcf2b54f3f304c6643d04d2c066d4ea6f5de4..2ce3fca545d3707ff4e0edc80b9708b157077780 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1808,6 +1808,17 @@ int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
                skb = skb_recv_udp(sk, 0, 1, &err);
                if (!skb)
                        return err;
+
+               if (udp_lib_checksum_complete(skb)) {
+                       __UDP_INC_STATS(sock_net(sk), UDP_MIB_CSUMERRORS,
+                                       IS_UDPLITE(sk));
+                       __UDP_INC_STATS(sock_net(sk), UDP_MIB_INERRORS,
+                                       IS_UDPLITE(sk));
+                       atomic_inc(&sk->sk_drops);
+                       kfree_skb(skb);
+                       continue;
+               }
+
                used = recv_actor(desc, skb, 0, skb->len);
                if (used <= 0) {
                        if (!copied)