NFS: Fix filehandle size comparisons in the mount code

Fix a sign issue in xdr_decode_fhstatus3()
Fix incorrect comparison in nfs_validate_mount_data()

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/mount_clnt.c b/fs/nfs/mount_clnt.c
index 49c7cd0..779d2eb 100644
--- a/fs/nfs/mount_clnt.c
+++ b/fs/nfs/mount_clnt.c
@@ -130,10 +130,11 @@
 				struct mnt_fhstatus *res)
 {
 	struct nfs_fh *fh = res->fh;
+	unsigned size;
 
 	if ((res->status = ntohl(*p++)) == 0) {
-		int size = ntohl(*p++);
-		if (size <= NFS3_FHSIZE) {
+		size = ntohl(*p++);
+		if (size <= NFS3_FHSIZE && size != 0) {
 			fh->size = size;
 			memcpy(fh->data, p, size);
 		} else