Patch "dccp: check sk for closed state in dccp_sendmsg()" has been added to the 4.15-stable tree

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

dccp: check sk for closed state in dccp_sendmsg()

to the 4.15-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:
dccp-check-sk-for-closed-state-in-dccp_sendmsg.patch
and it can be found in the queue-4.15 subdirectory.

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

From: Alexey Kodanev <[email protected]>
Date: Tue, 6 Mar 2018 22:57:01 +0300
Subject: dccp: check sk for closed state in dccp_sendmsg()

From: Alexey Kodanev <[email protected]>

[ Upstream commit 67f93df79aeefc3add4e4b31a752600f834236e2 ]

dccp_disconnect() sets 'dp->dccps_hc_tx_ccid' tx handler to NULL, therefore if DCCP socket is disconnected and dccp_sendmsg() is called after it, it will cause a NULL pointer dereference in dccp_write_xmit().

This crash and the reproducer was reported by syzbot. Looks like it is reproduced if commit 69c64866ce07 ("dccp: CVE-2017-8824:
use-after-free in DCCP code") is applied.

---
 net/dccp/proto.c |    5 +++++
 1 file changed, 5 insertions(+)

@@ -789,6 +789,11 @@ int dccp_sendmsg(struct sock *sk, struct
 	if (skb == NULL)
 		goto out_release;
 
+	if (sk->sk_state == DCCP_CLOSED) {
+		rc = -ENOTCONN;
+		goto out_discard;
+	}
+
 	skb_reserve(skb, sk->sk_prot->max_header);
 	rc = memcpy_from_msg(skb_put(skb, len), msg, len);
 	if (rc != 0)

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

queue-4.15/sch_netem-fix-skb-leak-in-netem_enqueue.patch queue-4.15/macvlan-filter-out-unsupported-feature-flags.patch queue-4.15/dccp-check-sk-for-closed-state-in-dccp_sendmsg.patch