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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiumei Mu <xmu@redhat.com>,
        Xin Long <lucien.xin@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.19 067/243] sctp: count sk_wmem_alloc by skb truesize in sctp_packet_transmit
Date:   Wed, 11 Dec 2019 16:03:49 +0100
Message-Id: <20191211150343.622625855@linuxfoundation.org>
In-Reply-To: <20191211150339.185439726@linuxfoundation.org>
References: <20191211150339.185439726@linuxfoundation.org>
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From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 02968ccf0125d39b08ecef5946300a8a873c0942 ]

Now sctp increases sk_wmem_alloc by 1 when doing set_owner_w for the
skb allocked in sctp_packet_transmit and decreases by 1 when freeing
this skb.

But when this skb goes through networking stack, some subcomponents
might change skb->truesize and add the same amount on sk_wmem_alloc.
However sctp doesn't know the amount to decrease by, it would cause
a leak on sk->sk_wmem_alloc and the sock can never be freed.

Xiumei found this issue when it hit esp_output_head() by using sctp
over ipsec, where skb->truesize is added and so is sk->sk_wmem_alloc.

Since sctp has used sk_wmem_queued to count for writable space since
Commit cd305c74b0f8 ("sctp: use sk_wmem_queued to check for writable
space"), it's ok to fix it by counting sk_wmem_alloc by skb truesize
in sctp_packet_transmit.

Fixes: cac2661c53f3 ("esp4: Avoid skb_cow_data whenever possible")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sctp/output.c | 21 +--------------------
 1 file changed, 1 insertion(+), 20 deletions(-)

diff --git a/net/sctp/output.c b/net/sctp/output.c
index 08601223b0bfa..b0e74a3e77ec5 100644
--- a/net/sctp/output.c
+++ b/net/sctp/output.c
@@ -399,25 +399,6 @@ finish:
 	return retval;
 }
 
-static void sctp_packet_release_owner(struct sk_buff *skb)
-{
-	sk_free(skb->sk);
-}
-
-static void sctp_packet_set_owner_w(struct sk_buff *skb, struct sock *sk)
-{
-	skb_orphan(skb);
-	skb->sk = sk;
-	skb->destructor = sctp_packet_release_owner;
-
-	/*
-	 * The data chunks have already been accounted for in sctp_sendmsg(),
-	 * therefore only reserve a single byte to keep socket around until
-	 * the packet has been transmitted.
-	 */
-	refcount_inc(&sk->sk_wmem_alloc);
-}
-
 static void sctp_packet_gso_append(struct sk_buff *head, struct sk_buff *skb)
 {
 	if (SCTP_OUTPUT_CB(head)->last == head)
@@ -604,7 +585,7 @@ int sctp_packet_transmit(struct sctp_packet *packet, gfp_t gfp)
 	if (!head)
 		goto out;
 	skb_reserve(head, packet->overhead + MAX_HEADER);
-	sctp_packet_set_owner_w(head, sk);
+	skb_set_owner_w(head, sk);
 
 	/* set sctp header */
 	sh = skb_push(head, sizeof(struct sctphdr));
-- 
2.20.1