Patch "sctp: add the missing sock_owned_by_user check in sctp_icmp_redirect" has been added to the 4.4-stable tree

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

sctp: add the missing sock_owned_by_user check in sctp_icmp_redirect

to the 4.4-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-add-the-missing-sock_owned_by_user-check-in-sctp_icmp_redirect.patch
and it can be found in the queue-4.4 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: Wed, 18 Oct 2017 21:37:49 +0800
Subject: sctp: add the missing sock_owned_by_user check in sctp_icmp_redirect

From: Xin Long <[email protected]>

[ Upstream commit 1cc276cec9ec574d41cf47dfc0f51406b6f26ab4 ]

Now sctp processes icmp redirect packet in sctp_icmp_redirect where it calls sctp_transport_dst_check in which tp->dst can be released.

The problem is before calling sctp_transport_dst_check, it doesn't check sock_owned_by_user, which means tp->dst could be freed while a process is accessing it with owning the socket.

An use-after-free issue could be triggered by this.

This patch is to fix it by checking sock_owned_by_user before calling sctp_transport_dst_check in sctp_icmp_redirect, so that it would not release tp->dst if users still hold sock lock.

Besides, the same issue fixed in commit 45caeaa5ac0b ("dccp/tcp: fix routing redirect race") on sctp also needs this check.

---
 net/sctp/input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -420,7 +420,7 @@ void sctp_icmp_redirect(struct sock *sk,
 {
 	struct dst_entry *dst;
 
-	if (!t)
+	if (sock_owned_by_user(sk) || !t)
 		return;
 	dst = sctp_transport_dst_check(t);
 	if (dst)

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

queue-4.4/sctp-reset-owner-sk-for-data-chunks-on-out-queues-when-migrating-a-sock.patch queue-4.4/sctp-add-the-missing-sock_owned_by_user-check-in-sctp_icmp_redirect.patch queue-4.4/ip6_gre-only-increase-err_count-for-some-certain-type-icmpv6-in-ip6gre_err.patch