crypto: atmel-tdes - Detecting in-place operations with two sg lists

Avoiding detecting finely in-place operations with different
scatter lists. Copying the source data for decryption into rctx->lastc
regardless if the operation is in-place or not. This allows in-place
operations with different scatter lists without affecting other
operations.

This approach takes less resources than parsing both scatter lists to
check if they are equal.
Signed-off-by: Ryan Wanner <Ryan.Wanner@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/atmel-tdes.c

@@ -565,17 +565,12 @@ atmel_tdes_set_iv_as_last_ciphertext_block(struct atmel_tdes_dev *dd)
 	if (req->cryptlen < ivsize)
 		return;
 
-	if (rctx->mode & TDES_FLAGS_ENCRYPT) {
+	if (rctx->mode & TDES_FLAGS_ENCRYPT)
 		scatterwalk_map_and_copy(req->iv, req->dst,
 					 req->cryptlen - ivsize, ivsize, 0);
-	} else {
-		if (req->src == req->dst)
-			memcpy(req->iv, rctx->lastc, ivsize);
-		else
-			scatterwalk_map_and_copy(req->iv, req->src,
-						 req->cryptlen - ivsize,
-						 ivsize, 0);
-	}
+	else
+		memcpy(req->iv, rctx->lastc, ivsize);
+
 }
 
 static void atmel_tdes_finish_req(struct atmel_tdes_dev *dd, int err)
@@ -722,7 +717,7 @@ static int atmel_tdes_crypt(struct skcipher_request *req, unsigned long mode)
 	rctx->mode = mode;
 
 	if ((mode & TDES_FLAGS_OPMODE_MASK) != TDES_FLAGS_ECB &&
-	    !(mode & TDES_FLAGS_ENCRYPT) && req->src == req->dst) {
+	    !(mode & TDES_FLAGS_ENCRYPT)) {
 		unsigned int ivsize = crypto_skcipher_ivsize(skcipher);
 
 		if (req->cryptlen >= ivsize)