Subject: [PATCH 32/37] net/tls: Only attach to sockets in ESTABLISHED state

From: Ilya Lesokhin <[email-masked]>
Date: Tue, 16 Jan 2018 15:31:52 +0200

[ Upstream commit d91c3e17f75f218022140dee18cf515292184a8f ]

Calling accept on a TCP socket with a TLS ulp attached results
in two sockets that share the same ulp context.
The ulp context is freed while a socket is destroyed, so
after one of the sockets is released, the second second will
trigger a use after free when it tries to access the ulp context
attached to it.
We restrict the TLS ulp to sockets in ESTABLISHED state
to prevent the scenario above.

Fixes: 3c4d7559159b ("tls: kernel TLS support")
Reported-by: [email-masked]
Signed-off-by: Ilya Lesokhin <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/tls/tls_main.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 60aff60e30ad..70757098f79b 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -444,6 +444,15 @@ static int tls_init(struct sock *sk)
 	struct tls_context *ctx;
 	int rc = 0;
 
+	/* The TLS ulp is currently supported only for TCP sockets
+	 * in ESTABLISHED state.
+	 * Supporting sockets in LISTEN state will require us
+	 * to modify the accept implementation to clone rather then
+	 * share the ulp context.
+	 */
+	if (sk->sk_state != TCP_ESTABLISHED)
+		return -ENOTSUPP;
+
 	/* allocate tls context */
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx) {
-- 
2.14.3