[PATCH v2 3/4] crypto: inside-secure - only update the result buffer when provided

[Antoine Tenart <antoine.tenart@free-electrons.com>]

The patch fixes the ahash support by only updating the result buffer
when provided. Otherwise the driver could crash with NULL pointer
exceptions, because the ahash caller isn't required to supply a result
buffer on all calls.

Fixes: 1b44c5a60c13 ("crypto: inside-secure - add SafeXcel EIP197 crypto engine driver")
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
---
 drivers/crypto/inside-secure/safexcel_hash.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/crypto/inside-secure/safexcel_hash.c b/drivers/crypto/inside-secure/safexcel_hash.c
index 6135c9f5742c..424f4c5d4d25 100644
--- a/drivers/crypto/inside-secure/safexcel_hash.c
+++ b/drivers/crypto/inside-secure/safexcel_hash.c
@@ -150,7 +150,12 @@ static int safexcel_handle_req_result(struct safexcel_crypto_priv *priv, int rin
 
 	if (sreq->finish)
 		result_sz = crypto_ahash_digestsize(ahash);
-	memcpy(sreq->state, areq->result, result_sz);
+
+	/* The called isn't required to supply a result buffer. Updated it only
+	 * when provided.
+	 */
+	if (areq->result)
+		memcpy(sreq->state, areq->result, result_sz);
 
 	dma_unmap_sg(priv->dev, areq->src,
 		     sg_nents_for_len(areq->src, areq->nbytes), DMA_TO_DEVICE);
-- 
2.14.3