crypto: cts - Weed out non-CBC algorithms

The cts algorithm as currently implemented assumes the underlying
is a CBC-mode algorithm.  So this patch adds a check for that to
eliminate bogus combinations of cts with non-CBC modes.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
diff --git a/crypto/cts.c b/crypto/cts.c
index 6a8089c..e467ec0 100644
--- a/crypto/cts.c
+++ b/crypto/cts.c
@@ -290,6 +290,9 @@
 	if (!is_power_of_2(alg->cra_blocksize))
 		goto out_put_alg;
 
+	if (strncmp(alg->cra_name, "cbc(", 4))
+		goto out_put_alg;
+
 	inst = crypto_alloc_instance("cts", alg);
 	if (IS_ERR(inst))
 		goto out_put_alg;