netdev - [PATCH v2 net-next 1/2] kcm: Only allow TCP sockets to be attached to a KCM mux

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Message-Id: <20180124203541.3172-2-tom@quantonium.net>
Date:   Wed, 24 Jan 2018 12:35:40 -0800
From:   Tom Herbert <tom@...ntonium.net>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, rohit@...ntonium.net, jchapman@...alix.com,
        g.nault@...halink.fr, Tom Herbert <tom@...ntonium.net>
Subject: [PATCH v2 net-next 1/2] kcm: Only allow TCP sockets to be attached to a KCM mux

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@...kaller.appspotmail.com
Signed-off-by: Tom Herbert <tom@...ntonium.net>
---
 net/kcm/kcmsock.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c
index d4e98f20fc2a..7632797fb68e 100644
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -1387,8 +1387,13 @@ static int kcm_attach(struct socket *sock, struct socket *csock,
 	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);
-- 
2.11.0