[CRYPTO]: Fix digest.c kmapping sg entries > page in length.

Below is the patch, against 2.6.7-rc2, to fix crypto/digest.c to do
multiple kmap()/kunmap() for scatterlist entries which have a size
greater than a single page, originally found and fixed by
N.C.Krishna Murthy <krmurthy@cisco.com>.
Signed-off-by: Clay Haapala <chaapala@cisco.com>
Signed-off-by: David S. Miller <davem@redhat.com>

crypto/digest.c

@@ -29,11 +29,26 @@ static void update(struct crypto_tfm *tfm,
 	unsigned int i;
 
 	for (i = 0; i < nsg; i++) {
-		char *p = crypto_kmap(sg[i].page, 0) + sg[i].offset;
-		tfm->__crt_alg->cra_digest.dia_update(crypto_tfm_ctx(tfm),
-		                                      p, sg[i].length);
+
+		struct page *pg = sg[i].page;
+		unsigned int offset = sg[i].offset;
+		unsigned int l = sg[i].length;
+
+		do {
+			unsigned int bytes_from_page = min(l, ((unsigned int)
+							   (PAGE_SIZE)) - 
+							   offset);
+			char *p = crypto_kmap(pg, 0) + offset;
+
+			tfm->__crt_alg->cra_digest.dia_update
+					(crypto_tfm_ctx(tfm), p,
+					 bytes_from_page);
 			crypto_kunmap(p, 0);
 			crypto_yield(tfm);
+			offset = 0;
+			pg++;
+			l -= bytes_from_page;
+		} while (l > 0);
 	}
 }