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>

fs/nfs/nfs2xdr.c

@@ -290,8 +290,13 @@ static int decode_fattr(struct xdr_stream *xdr, struct nfs_fattr *fattr)
 
 	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 @@ static int decode_fattr(struct xdr_stream *xdr, struct nfs_fattr *fattr)
 	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 @@ static void encode_sattr(struct xdr_stream *xdr, const struct iattr *attr)
 	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)