crypto: hash - initialize entry len for null input in crypto hash sg list walk

For the special case when we have a null input string, we want
to initialize the entry len to 0 for the hash/ahash walk, so
cyrpto_hash_walk_last will return the correct result indicating
that we have completed the scatter list walk.  Otherwise we may
keep walking the sg list and access bogus memory address.
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/ahash.c

@@ -131,8 +131,10 @@ int crypto_hash_walk_first(struct ahash_request *req,
 {
 	walk->total = req->nbytes;
 
-	if (!walk->total)
+	if (!walk->total) {
+		walk->entrylen = 0;
 		return 0;
+	}
 
 	walk->alignmask = crypto_ahash_alignmask(crypto_ahash_reqtfm(req));
 	walk->sg = req->src;
@@ -147,8 +149,10 @@ int crypto_ahash_walk_first(struct ahash_request *req,
 {
 	walk->total = req->nbytes;
 
-	if (!walk->total)
+	if (!walk->total) {
+		walk->entrylen = 0;
 		return 0;
+	}
 
 	walk->alignmask = crypto_ahash_alignmask(crypto_ahash_reqtfm(req));
 	walk->sg = req->src;
@@ -167,8 +171,10 @@ int crypto_hash_walk_first_compat(struct hash_desc *hdesc,
 {
 	walk->total = len;
 
-	if (!walk->total)
+	if (!walk->total) {
+		walk->entrylen = 0;
 		return 0;
+	}
 
 	walk->alignmask = crypto_hash_alignmask(hdesc->tfm);
 	walk->sg = sg;