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 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: dccp-check-sk-for-closed-state-in-dccp_sendmsg.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Mar 29 08:33:08 CEST 2018

From: Alexey Kodanev alexey.kodanev@oracle.com Date: Tue, 6 Mar 2018 22:57:01 +0300 Subject: dccp: check sk for closed state in dccp_sendmsg()

From: Alexey Kodanev alexey.kodanev@oracle.com

[ 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.

Reported-by: syzbot+f99ab3887ab65d70f816@syzkaller.appspotmail.com Signed-off-by: Alexey Kodanev alexey.kodanev@oracle.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/dccp/proto.c | 5 +++++ 1 file changed, 5 insertions(+)

--- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -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 alexey.kodanev@oracle.com are

queue-4.4/dccp-check-sk-for-closed-state-in-dccp_sendmsg.patch