nfs: Convert nfs2xdr to use kuids and kgids

When reading uids and gids off the wire convert them to
kuids and kgids.

When putting kuids and kgids onto the wire first convert
them to uids and gids the other side will understand.

Add an additional failure mode for incoming uid or
gids that are invalid.

Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 06b9df4..62db136 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -290,8 +290,13 @@
 
 	fattr->mode = be32_to_cpup(p++);
 	fattr->nlink = be32_to_cpup(p++);
-	fattr->uid = be32_to_cpup(p++);
-	fattr->gid = be32_to_cpup(p++);
+	fattr->uid = make_kuid(&init_user_ns, be32_to_cpup(p++));
+	if (!uid_valid(fattr->uid))
+		goto out_uid;
+	fattr->gid = make_kgid(&init_user_ns, be32_to_cpup(p++));
+	if (!gid_valid(fattr->gid))
+		goto out_gid;
+		
 	fattr->size = be32_to_cpup(p++);
 	fattr->du.nfs2.blocksize = be32_to_cpup(p++);
 
@@ -313,6 +318,12 @@
 	fattr->change_attr = nfs_timespec_to_change_attr(&fattr->ctime);
 
 	return 0;
+out_uid:
+	dprintk("NFS: returned invalid uid\n");
+	return -EINVAL;
+out_gid:
+	dprintk("NFS: returned invalid gid\n");
+	return -EINVAL;
 out_overflow:
 	print_overflow_msg(__func__, xdr);
 	return -EIO;
@@ -351,11 +362,11 @@
 	else
 		*p++ = cpu_to_be32(NFS2_SATTR_NOT_SET);
 	if (attr->ia_valid & ATTR_UID)
-		*p++ = cpu_to_be32(attr->ia_uid);
+		*p++ = cpu_to_be32(from_kuid(&init_user_ns, attr->ia_uid));
 	else
 		*p++ = cpu_to_be32(NFS2_SATTR_NOT_SET);
 	if (attr->ia_valid & ATTR_GID)
-		*p++ = cpu_to_be32(attr->ia_gid);
+		*p++ = cpu_to_be32(from_kgid(&init_user_ns, attr->ia_gid));
 	else
 		*p++ = cpu_to_be32(NFS2_SATTR_NOT_SET);
 	if (attr->ia_valid & ATTR_SIZE)