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 bae5c4ec5786a55569fdd30005954e5c67a9be08..42d4af6324950ac6fcda893b5fb98666ebc6a3bb 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1912,11 +1912,13 @@ 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);