cifs: teach signing routines how to deal with arrays of pages in a smb_rqst

Use the smb_send_rqst helper function to kmap each page in the array
and update the hash for that chunk.

Reviewed-by: Pavel Shilovsky <pshilovsky@samba.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index af52052..652f505 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -29,6 +29,7 @@
 #include "ntlmssp.h"
 #include <linux/ctype.h>
 #include <linux/random.h>
+#include <linux/highmem.h>
 
 /*
  * Calculate and return the CIFS signature based on the mac key and SMB PDU.
@@ -93,6 +94,16 @@
 		}
 	}
 
+	/* now hash over the rq_pages array */
+	for (i = 0; i < rqst->rq_npages; i++) {
+		struct kvec p_iov;
+
+		cifs_rqst_page_to_kvec(rqst, i, &p_iov);
+		crypto_shash_update(&server->secmech.sdescmd5->shash,
+					p_iov.iov_base, p_iov.iov_len);
+		kunmap(rqst->rq_pages[i]);
+	}
+
 	rc = crypto_shash_final(&server->secmech.sdescmd5->shash, signature);
 	if (rc)
 		cERROR(1, "%s: Could not generate md5 hash", __func__);