crypto: sahara - fix cbc selftest failure

The kernel crypto API requires that all CBC implementations update the IV
buffer to contain the last ciphertext block.

This fixes the following cbc selftest error:
alg: skcipher: sahara-cbc-aes encryption test failed (wrong output IV) on
test vector 0, cfg="in-place (one sglist)"

Fixes: 5de88752 ("crypto: sahara - Add driver for SAHARA2 accelerator.")
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/sahara.c

@@ -148,6 +148,7 @@ struct sahara_ctx {
 
 struct sahara_aes_reqctx {
 	unsigned long mode;
+	u8 iv_out[AES_BLOCK_SIZE];
 	struct skcipher_request fallback_req;	// keep at the end
 };
 
@@ -541,8 +542,24 @@ static int sahara_hw_descriptor_create(struct sahara_dev *dev)
 	return -EINVAL;
 }
 
+static void sahara_aes_cbc_update_iv(struct skcipher_request *req)
+{
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
+	struct sahara_aes_reqctx *rctx = skcipher_request_ctx(req);
+	unsigned int ivsize = crypto_skcipher_ivsize(skcipher);
+
+	/* Update IV buffer to contain the last ciphertext block */
+	if (rctx->mode & FLAGS_ENCRYPT) {
+		sg_pcopy_to_buffer(req->dst, sg_nents(req->dst), req->iv,
+				   ivsize, req->cryptlen - ivsize);
+	} else {
+		memcpy(req->iv, rctx->iv_out, ivsize);
+	}
+}
+
 static int sahara_aes_process(struct skcipher_request *req)
 {
+	struct crypto_skcipher *skcipher = crypto_skcipher_reqtfm(req);
 	struct sahara_dev *dev = dev_ptr;
 	struct sahara_ctx *ctx;
 	struct sahara_aes_reqctx *rctx;
@@ -564,8 +581,17 @@ static int sahara_aes_process(struct skcipher_request *req)
 	rctx->mode &= FLAGS_MODE_MASK;
 	dev->flags = (dev->flags & ~FLAGS_MODE_MASK) | rctx->mode;
 
-	if ((dev->flags & FLAGS_CBC) && req->iv)
-		memcpy(dev->iv_base, req->iv, AES_KEYSIZE_128);
+	if ((dev->flags & FLAGS_CBC) && req->iv) {
+		unsigned int ivsize = crypto_skcipher_ivsize(skcipher);
+
+		memcpy(dev->iv_base, req->iv, ivsize);
+
+		if (!(dev->flags & FLAGS_ENCRYPT)) {
+			sg_pcopy_to_buffer(req->src, sg_nents(req->src),
+					   rctx->iv_out, ivsize,
+					   req->cryptlen - ivsize);
+		}
+	}
 
 	/* assign new context to device */
 	dev->ctx = ctx;
@@ -588,6 +614,9 @@ static int sahara_aes_process(struct skcipher_request *req)
 	dma_unmap_sg(dev->device, dev->in_sg, dev->nb_in_sg,
 		DMA_TO_DEVICE);
 
+	if ((dev->flags & FLAGS_CBC) && req->iv)
+		sahara_aes_cbc_update_iv(req);
+
 	return 0;
 }