crypto: qce - Return error for zero length messages

Crypto engine BAM dma does not support 0 length data. Return unsupported
if zero length messages are passed for transformation.
Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/qce/skcipher.c

@@ -8,6 +8,7 @@
 #include <linux/interrupt.h>
 #include <linux/moduleparam.h>
 #include <linux/types.h>
+#include <linux/errno.h>
 #include <crypto/aes.h>
 #include <crypto/internal/des.h>
 #include <crypto/internal/skcipher.h>
@@ -260,6 +261,10 @@ static int qce_skcipher_crypt(struct skcipher_request *req, int encrypt)
 	rctx->flags |= encrypt ? QCE_ENCRYPT : QCE_DECRYPT;
 	keylen = IS_XTS(rctx->flags) ? ctx->enc_keylen >> 1 : ctx->enc_keylen;
 
+	/* CE does not handle 0 length messages */
+	if (!req->cryptlen)
+		return 0;
+
 	/* qce is hanging when AES-XTS request len > QCE_SECTOR_SIZE and
 	 * is not a multiple of it; pass such requests to the fallback
 	 */