linux-kernel - [PATCH] sctp: fix refcount bug in sctp

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Message-Id: <1584330804-18477-1-git-send-email-hqjagain@gmail.com>
Date:   Mon, 16 Mar 2020 11:53:24 +0800
From:   Qiujun Huang <hqjagain@...il.com>
To:     vyasevich@...il.com, nhorman@...driver.com,
        marcelo.leitner@...il.com, davem@...emloft.net, kuba@...nel.org
Cc:     linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Qiujun Huang <hqjagain@...il.com>
Subject: [PATCH] sctp: fix refcount bug in sctp_wfree

Do accounting for skb's real sk.
In some case skb->sk != asoc->base.sk.

Reported-and-tested-by: syzbot+cea71eec5d6de256d54d@...kaller.appspotmail.com
Signed-off-by: Qiujun Huang <hqjagain@...il.com>
---
 net/sctp/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 1b56fc4..5f5c28b 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9080,7 +9080,7 @@ static void sctp_wfree(struct sk_buff *skb)
 {
 	struct sctp_chunk *chunk = skb_shinfo(skb)->destructor_arg;
 	struct sctp_association *asoc = chunk->asoc;
-	struct sock *sk = asoc->base.sk;
+	struct sock *sk = skb->sk;
 
 	sk_mem_uncharge(sk, skb->truesize);
 	sk->sk_wmem_queued -= skb->truesize + sizeof(struct sctp_chunk);
@@ -9109,7 +9109,7 @@ static void sctp_wfree(struct sk_buff *skb)
 	}
 
 	sock_wfree(skb);
-	sctp_wake_up_waiters(sk, asoc);
+	sctp_wake_up_waiters(asoc->base.sk, asoc);
 
 	sctp_association_put(asoc);
 }
-- 
1.8.3.1