[PATCH 4.19 067/243] sctp: count sk_wmem_alloc by skb truesize in sctp_packet_transmit

From: Greg Kroah-Hartman
Date: Wed Dec 11 2019 - 10:52:35 EST

From: Xin Long <lucien.xin@xxxxxxxxx>

[ 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@xxxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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));