crypto: sahara - fix processing requests with cryptlen < sg->length

It's not always the case that the entire sg entry needs to be processed.
Currently, when cryptlen is less than sg->legth, "Descriptor length" errors
are encountered.

The error was noticed when testing xts(sahara-ecb-aes) with arbitrary sized
input data. To fix this, take the actual request size into account when
populating the hw links.

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

@@ -444,6 +444,7 @@ static int sahara_hw_descriptor_create(struct sahara_dev *dev)
 	int ret;
 	int i, j;
 	int idx = 0;
+	u32 len;
 
 	memcpy(dev->key_base, ctx->key, ctx->keylen);
 
@@ -494,12 +495,14 @@ static int sahara_hw_descriptor_create(struct sahara_dev *dev)
 	/* Create input links */
 	dev->hw_desc[idx]->p1 = dev->hw_phys_link[0];
 	sg = dev->in_sg;
+	len = dev->total;
 	for (i = 0; i < dev->nb_in_sg; i++) {
-		dev->hw_link[i]->len = sg->length;
+		dev->hw_link[i]->len = min(len, sg->length);
 		dev->hw_link[i]->p = sg->dma_address;
 		if (i == (dev->nb_in_sg - 1)) {
 			dev->hw_link[i]->next = 0;
 		} else {
+			len -= min(len, sg->length);
 			dev->hw_link[i]->next = dev->hw_phys_link[i + 1];
 			sg = sg_next(sg);
 		}
@@ -508,12 +511,14 @@ static int sahara_hw_descriptor_create(struct sahara_dev *dev)
 	/* Create output links */
 	dev->hw_desc[idx]->p2 = dev->hw_phys_link[i];
 	sg = dev->out_sg;
+	len = dev->total;
 	for (j = i; j < dev->nb_out_sg + i; j++) {
-		dev->hw_link[j]->len = sg->length;
+		dev->hw_link[j]->len = min(len, sg->length);
 		dev->hw_link[j]->p = sg->dma_address;
 		if (j == (dev->nb_out_sg + i - 1)) {
 			dev->hw_link[j]->next = 0;
 		} else {
+			len -= min(len, sg->length);
 			dev->hw_link[j]->next = dev->hw_phys_link[j + 1];
 			sg = sg_next(sg);
 		}