Commit 02968ccf authored Nov 18, 2018 by Xin Long Committed by David S. Miller Nov 19, 2018

sctp: count sk_wmem_alloc by skb truesize in sctp_packet_transmit



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 cd305c74 ("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: cac2661c ("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>

parent a36b5444

net/sctp/output.c

+1 −20

Original line number	Diff line number	Diff line
		@@ -396,25 +396,6 @@ 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)
		@@ -601,7 +582,7 @@ 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));

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