From: Lu Wei <luwei32@huawei.com>
Date: Fri, 21 Oct 2022 04:06:22 +0000 (+0800)
Subject: tcp: fix a signed-integer-overflow bug in tcp_add_backlog()
X-Git-Tag: v6.0.7~54
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=28addf029417d53b1df062b4c87feb7bc033cb5f;p=thirdparty%2Fkernel%2Fstable.git

tcp: fix a signed-integer-overflow bug in tcp_add_backlog()

[ Upstream commit ec791d8149ff60c40ad2074af3b92a39c916a03f ]

The type of sk_rcvbuf and sk_sndbuf in struct sock is int, and
in tcp_add_backlog(), the variable limit is caculated by adding
sk_rcvbuf, sk_sndbuf and 64 * 1024, it may exceed the max value
of int and overflow. This patch reduces the limit budget by
halving the sndbuf to solve this issue since ACK packets are much
smaller than the payload.

Fixes: c9c3321257e1 ("tcp: add tcp_add_backlog()")
Signed-off-by: Lu Wei <luwei32@huawei.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5b019ba2b9d21..fe9a6022db66d 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1853,11 +1853,13 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
 	__skb_push(skb, hdrlen);
 
 no_coalesce:
+	limit = (u32)READ_ONCE(sk->sk_rcvbuf) + (u32)(READ_ONCE(sk->sk_sndbuf) >> 1);
+
 	/* Only socket owner can try to collapse/prune rx queues
 	 * to reduce memory overhead, so add a little headroom here.
 	 * Few sockets backlog are possibly concurrently non empty.
 	 */
-	limit = READ_ONCE(sk->sk_rcvbuf) + READ_ONCE(sk->sk_sndbuf) + 64*1024;
+	limit += 64 * 1024;
 
 	if (unlikely(sk_add_backlog(sk, skb, limit))) {
 		bh_unlock_sock(sk);