diff --git a/crypto/cts.c b/crypto/cts.c
index 4e28d83ae37d..9441da797bb9 100644
--- a/crypto/cts.c
+++ b/crypto/cts.c
@@ -152,12 +152,14 @@ static int crypto_cts_encrypt(struct skcipher_request *req)
 	struct skcipher_request *subreq = &rctx->subreq;
 	int bsize = crypto_skcipher_blocksize(tfm);
 	unsigned int nbytes = req->cryptlen;
-	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
 	unsigned int offset;
 
 	skcipher_request_set_tfm(subreq, ctx->child);
 
-	if (cbc_blocks <= 0) {
+	if (nbytes < bsize)
+		return -EINVAL;
+
+	if (nbytes == bsize) {
 		skcipher_request_set_callback(subreq, req->base.flags,
 					      req->base.complete,
 					      req->base.data);
@@ -166,7 +168,7 @@ static int crypto_cts_encrypt(struct skcipher_request *req)
 		return crypto_skcipher_encrypt(subreq);
 	}
 
-	offset = cbc_blocks * bsize;
+	offset = rounddown(nbytes - 1, bsize);
 	rctx->offset = offset;
 
 	skcipher_request_set_callback(subreq, req->base.flags,
@@ -244,13 +246,15 @@ static int crypto_cts_decrypt(struct skcipher_request *req)
 	struct skcipher_request *subreq = &rctx->subreq;
 	int bsize = crypto_skcipher_blocksize(tfm);
 	unsigned int nbytes = req->cryptlen;
-	int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
 	unsigned int offset;
 	u8 *space;
 
 	skcipher_request_set_tfm(subreq, ctx->child);
 
-	if (cbc_blocks <= 0) {
+	if (nbytes < bsize)
+		return -EINVAL;
+
+	if (nbytes == bsize) {
 		skcipher_request_set_callback(subreq, req->base.flags,
 					      req->base.complete,
 					      req->base.data);
@@ -264,10 +268,10 @@ static int crypto_cts_decrypt(struct skcipher_request *req)
 
 	space = crypto_cts_reqctx_space(req);
 
-	offset = cbc_blocks * bsize;
+	offset = rounddown(nbytes - 1, bsize);
 	rctx->offset = offset;
 
-	if (cbc_blocks <= 1)
+	if (offset <= bsize)
 		memcpy(space, req->iv, bsize);
 	else
 		scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,