linux-kernel - [PATCH 5.15 140/279] udp: Validate checksum in udp_read

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Message-Id: <20211124115723.620795552@linuxfoundation.org>
Date:   Wed, 24 Nov 2021 12:57:07 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Daniel Borkmann <daniel@...earbox.net>,
        Cong Wang <cong.wang@...edance.com>,
        John Fastabend <john.fastabend@...il.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 140/279] udp: Validate checksum in udp_read_sock()

From: Cong Wang <cong.wang@...edance.com>

[ 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@...earbox.net>
Signed-off-by: Cong Wang <cong.wang@...edance.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: John Fastabend <john.fastabend@...il.com>
Link: https://lore.kernel.org/bpf/20211115044006.26068-1-xiyou.wangcong@gmail.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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