Patch "sctp: return next obj by passing pos + 1 into sctp_transport_get_idx" has been added to the 4.9-stable tree

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

sctp: return next obj by passing pos + 1 into sctp_transport_get_idx

to the 4.9-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-return-next-obj-by-passing-pos-1-into-sctp_transport_get_idx.patch
and it can be found in the queue-4.9 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: Thu, 15 Jun 2017 17:49:08 +0800
Subject: sctp: return next obj by passing pos + 1 into sctp_transport_get_idx

From: Xin Long <[email protected]>

[ Upstream commit 988c7322116970696211e902b468aefec95b6ec4 ]

In sctp_for_each_transport, pos is used to save how many objs it has dumped. Now it gets the last obj by sctp_transport_get_idx, then gets the next obj by sctp_transport_get_next.

The issue is that in the meanwhile if some objs in transport hashtable are removed and the objs nums are less than pos, sctp_transport_get_idx would return NULL and hti.walker.tbl is NULL as well. At this moment it should stop hti, instead of continue getting the next obj. Or it would cause a NULL pointer dereference in sctp_transport_get_next.

This patch is to pass pos + 1 into sctp_transport_get_idx to get the next obj directly, even if pos > objs nums, it would return NULL and stop hti.

---
 net/sctp/socket.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

@@ -4506,9 +4506,8 @@ int sctp_for_each_transport(int (*cb)(st
 	if (err)
 		return err;
 
-	sctp_transport_get_idx(net, &hti, pos);
-	obj = sctp_transport_get_next(net, &hti);
-	for (; obj && !IS_ERR(obj); obj = sctp_transport_get_next(net, &hti)) {
+	obj = sctp_transport_get_idx(net, &hti, pos + 1);
+	for (; !IS_ERR_OR_NULL(obj); obj = sctp_transport_get_next(net, &hti)) {
 		struct sctp_transport *transport = obj;
 
 		if (!sctp_transport_hold(transport))

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

queue-4.9/ipv6-fix-calling-in6_ifa_hold-incorrectly-for-dad-work.patch queue-4.9/igmp-acquire-pmc-lock-for-ip_mc_clear_src.patch queue-4.9/sctp-return-next-obj-by-passing-pos-1-into-sctp_transport_get_idx.patch queue-4.9/sctp-disable-bh-in-sctp_for_each_endpoint.patch