linux-kernel - [PATCH] sctp: Fix sk_buff leak when receiving a datagram

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Message-Id: <1592051965-94731-1-git-send-email-xiyuyang19@fudan.edu.cn>
Date:   Sat, 13 Jun 2020 20:39:25 +0800
From:   Xiyu Yang <xiyuyang19@...an.edu.cn>
To:     Vlad Yasevich <vyasevich@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-sctp@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     yuanxzhang@...an.edu.cn, kjlu@....edu,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>
Subject: [PATCH] sctp: Fix sk_buff leak when receiving a datagram

In sctp_skb_recv_datagram(), the function fetch a sk_buff object from
the receiving queue to "skb" by calling skb_peek() or __skb_dequeue()
and return its reference to the caller.

However, when calling __skb_dequeue() successfully, the function forgets
to hold a reference count of the "skb" object and directly return it,
causing a potential memory leak in the caller function.

Fix this issue by calling refcount_inc after __skb_dequeue()
successfully executed.

Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
---
 net/sctp/socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index d57e1a002ffc..4c8f0b83efd0 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -8990,6 +8990,8 @@ struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags,
 				refcount_inc(&skb->users);
 		} else {
 			skb = __skb_dequeue(&sk->sk_receive_queue);
+			if (skb)
+				refcount_inc(&skb->users);
 		}
 
 		if (skb)
-- 
2.7.4