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>
diff --git a/crypto/authenc.c b/crypto/authenc.c
index 05eb32e..b9884ee 100644
--- a/crypto/authenc.c
+++ b/crypto/authenc.c
@@ -181,6 +181,7 @@
 	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 @@
 		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 @@
 	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 @@
 	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 @@
 	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);