crypto: authenc - Fix cryptlen calculation

This patch (applied against 2.6.34) fixes the calculation of the
length of the ABLKCIPHER decrypt request ("cryptlen") after an
asynchronous hash request has been completed in the AUTHENC interface.

Signed-off-by: Shikhar Khattar <shikhark@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/authenc.c

@@ -181,6 +181,7 @@ static void authenc_verify_ahash_update_done(struct crypto_async_request *areq,
 	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
 	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
 	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
+	unsigned int cryptlen = req->cryptlen;
 
 	if (err)
 		goto out;
@@ -196,6 +197,7 @@ static void authenc_verify_ahash_update_done(struct crypto_async_request *areq,
 		goto out;
 
 	authsize = crypto_aead_authsize(authenc);
+	cryptlen -= authsize;
 	ihash = ahreq->result + authsize;
 	scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen,
 				 authsize, 0);
@@ -209,7 +211,7 @@ static void authenc_verify_ahash_update_done(struct crypto_async_request *areq,
 	ablkcipher_request_set_callback(abreq, aead_request_flags(req),
 					req->base.complete, req->base.data);
 	ablkcipher_request_set_crypt(abreq, req->src, req->dst,
-				     req->cryptlen, req->iv);
+				     cryptlen, req->iv);
 
 	err = crypto_ablkcipher_decrypt(abreq);
 
@@ -228,11 +230,13 @@ static void authenc_verify_ahash_done(struct crypto_async_request *areq,
 	struct crypto_authenc_ctx *ctx = crypto_aead_ctx(authenc);
 	struct authenc_request_ctx *areq_ctx = aead_request_ctx(req);
 	struct ahash_request *ahreq = (void *)(areq_ctx->tail + ctx->reqoff);
+	unsigned int cryptlen = req->cryptlen;
 
 	if (err)
 		goto out;
 
 	authsize = crypto_aead_authsize(authenc);
+	cryptlen -= authsize;
 	ihash = ahreq->result + authsize;
 	scatterwalk_map_and_copy(ihash, areq_ctx->sg, areq_ctx->cryptlen,
 				 authsize, 0);
@@ -246,7 +250,7 @@ static void authenc_verify_ahash_done(struct crypto_async_request *areq,
 	ablkcipher_request_set_callback(abreq, aead_request_flags(req),
 					req->base.complete, req->base.data);
 	ablkcipher_request_set_crypt(abreq, req->src, req->dst,
-				     req->cryptlen, req->iv);
+				     cryptlen, req->iv);
 
 	err = crypto_ablkcipher_decrypt(abreq);