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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+8865eaff7f9acd593945@syzkaller.appspotmail.com,
        Tom Herbert <tom@quantonium.net>,
        Eric Dumazet <edumazet@google.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.9 003/145] kcm: Only allow TCP sockets to be attached to a KCM mux
Date:   Fri, 23 Feb 2018 19:25:09 +0100
Message-Id: <20180223170725.169691035@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tom Herbert <tom@quantonium.net>

commit 581e7226a5d43f629eb6399a121f85f6a15f81be upstream.

TCP sockets for IPv4 and IPv6 that are not listeners or in closed
stated are allowed to be attached to a KCM mux.

Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module")
Reported-by: syzbot+8865eaff7f9acd593945@syzkaller.appspotmail.com
Signed-off-by: Tom Herbert <tom@quantonium.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/kcm/kcmsock.c |    9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1381,8 +1381,13 @@ static int kcm_attach(struct socket *soc
 	if (!csk)
 		return -EINVAL;
 
-	/* We must prevent loops or risk deadlock ! */
-	if (csk->sk_family == PF_KCM)
+	/* Only allow TCP sockets to be attached for now */
+	if ((csk->sk_family != AF_INET && csk->sk_family != AF_INET6) ||
+	    csk->sk_protocol != IPPROTO_TCP)
+		return -EOPNOTSUPP;
+
+	/* Don't allow listeners or closed sockets */
+	if (csk->sk_state == TCP_LISTEN || csk->sk_state == TCP_CLOSE)
 		return -EOPNOTSUPP;
 
 	psock = kmem_cache_zalloc(kcm_psockp, GFP_KERNEL);