Patch "sctp: fix the issue that a __u16 variable may overflow in sctp_ulpq_renege" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

sctp: fix the issue that a __u16 variable may overflow in sctp_ulpq_renege

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sctp-fix-the-issue-that-a-__u16-variable-may-overflow-in-sctp_ulpq_renege.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Xin Long <[email protected]>
Date: Mon, 18 Dec 2017 14:07:25 +0800
Subject: sctp: fix the issue that a __u16 variable may overflow in sctp_ulpq_renege

From: Xin Long <[email protected]>

[ Upstream commit 5c468674d17056148da06218d4da5d04baf22eac ]

Now when reneging events in sctp_ulpq_renege(), the variable freed could be increased by a __u16 value twice while freed is of __u16 type. It means freed may overflow at the second addition.

This patch is to fix it by using __u32 type for 'freed', while at it, also to remove 'if (chunk)' check, as all renege commands are generated in sctp_eat_data and it can't be NULL.

---
 net/sctp/ulpqueue.c |   24 ++++++++----------------
 1 file changed, 8 insertions(+), 16 deletions(-)

@@ -1084,29 +1084,21 @@ void sctp_ulpq_partial_delivery(struct s
 void sctp_ulpq_renege(struct sctp_ulpq *ulpq, struct sctp_chunk *chunk,
 		      gfp_t gfp)
 {
-	struct sctp_association *asoc;
-	__u16 needed, freed;
+	struct sctp_association *asoc = ulpq->asoc;
+	__u32 freed = 0;
+	__u16 needed;
 
-	asoc = ulpq->asoc;
-
-	if (chunk) {
-		needed = ntohs(chunk->chunk_hdr->length);
-		needed -= sizeof(struct sctp_data_chunk);
-	} else
-		needed = SCTP_DEFAULT_MAXWINDOW;
-
-	freed = 0;
+	needed = ntohs(chunk->chunk_hdr->length) -
+		 sizeof(struct sctp_data_chunk);
 
 	if (skb_queue_empty(&asoc->base.sk->sk_receive_queue)) {
 		freed = sctp_ulpq_renege_order(ulpq, needed);
-		if (freed < needed) {
+		if (freed < needed)
 			freed += sctp_ulpq_renege_frags(ulpq, needed - freed);
-		}
 	}
 	/* If able to free enough room, accept this chunk. */
-	if (chunk && (freed >= needed)) {
-		int retval;
-		retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
+	if (freed >= needed) {
+		int retval = sctp_ulpq_tail_data(ulpq, chunk, gfp);
 		/*
 		 * Enter partial delivery if chunk has not been
 		 * delivered; otherwise, drain the reassembly queue.

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/ip_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_gre-remove-the-incorrect-mtu-limit-for-ipgre-tap.patch queue-4.14/ip6_tunnel-allow-ip6gre-dev-mtu-to-be-set-below-1280.patch queue-4.14/vxlan-update-skb-dst-pmtu-on-tx-path.patch queue-4.14/ip6_tunnel-get-the-min-mtu-properly-in-ip6_tnl_xmit.patch queue-4.14/sctp-fix-the-issue-that-a-__u16-variable-may-overflow-in-sctp_ulpq_renege.patch