[PATCH 5.15 140/279] udp: Validate checksum in udp_read_sock()

[Greg Kroah-Hartman]

From: Cong Wang <cong.wang@xxxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxx>
Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Link: https://lore.kernel.org/bpf/20211115044006.26068-1-xiyou.wangcong@xxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/udp.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 2fffcf2b54f3f..2ce3fca545d37 100644
--- 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)
-- 
2.33.0