[PATCH 2/2] crypto: ecdh - fix ecdh_max_size

[Tudor Ambarus <tudor.ambarus@microchip.com>]

The function should return minimum size for output buffer
or error code if key hasn't been set.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
---
 crypto/ecdh.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index 63ca337..01bfd13 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -109,10 +109,10 @@ static int ecdh_compute_value(struct kpp_request *req)
 static int ecdh_max_size(struct crypto_kpp *tfm)
 {
 	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
-	int nbytes = ctx->ndigits << ECC_DIGITS_TO_BYTES_SHIFT;
 
-	/* Public key is made of two coordinates */
-	return 2 * nbytes;
+	/* Public key is made of two coordinates, add one to the left shift  */
+	return ctx->ndigits ? ctx->ndigits << (ECC_DIGITS_TO_BYTES_SHIFT + 1) :
+			      -EINVAL;
 }
 
 static void no_exit_tfm(struct crypto_kpp *tfm)
-- 
2.7.4