From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp2130.oracle.com ([156.151.31.86]:48242 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797AbeCFTwo (ORCPT ); Tue, 6 Mar 2018 14:52:44 -0500 From: Alexey Kodanev To: netdev@vger.kernel.org Cc: Eric Dumazet , David Miller , Alexey Kodanev Subject: [PATCH net] dccp: check sk for closed state in dccp_sendmsg() Date: Tue, 6 Mar 2018 22:57:01 +0300 Message-Id: <1520366221-12350-1-git-send-email-alexey.kodanev@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- net/dccp/proto.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/dccp/proto.c b/net/dccp/proto.c index 15bdc00..84cd4e3 100644 --- a/net/dccp/proto.c +++ b/net/dccp/proto.c @@ -794,6 +794,11 @@ int dccp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) 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) -- 1.8.3.1