daemon: check xfs label lengths (RHBZ#1162966).

Similar to commit 52f9cd4882, but for xfs
filesystems.

daemon/daemon.h

@@ -253,6 +253,10 @@ extern void main_loop (int sock) __attribute__((noreturn));
 /*-- in xattr.c --*/
 extern int copy_xattrs (const char *src, const char *dest);
 
+/*-- in xfs.c --*/
+/* Documented in xfs_admin(8). */
+#define XFS_LABEL_MAX 12
+
 /* ordinary daemon functions use these to indicate errors
  * NB: you don't need to prefix the string with the current command,
  * it is added automatically by the client-side RPC stubs.

daemon/labels.c

@@ -118,6 +118,12 @@ xfslabel (const char *device, const char *label)
     return -1;
   }
 
+  if (strlen (label) > XFS_LABEL_MAX) {
+    reply_with_error ("%s: xfs labels are limited to %d bytes",
+                      label, XFS_LABEL_MAX);
+    return -1;
+  }
+
   r = command (NULL, &err, str_xfs_admin, "-L", label, device, NULL);
   if (r == -1) {
     reply_with_error ("%s", err);

daemon/xfs.c

@@ -498,6 +498,12 @@ do_xfs_admin (const char *device,
   }
 
   if (optargs_bitmask & GUESTFS_XFS_ADMIN_LABEL_BITMASK) {
+    if (strlen (label) > XFS_LABEL_MAX) {
+      reply_with_error ("%s: xfs labels are limited to %d bytes",
+                        label, XFS_LABEL_MAX);
+      return -1;
+    }
+
     ADD_ARG (argv, i, "-L");
     ADD_ARG (argv, i, label);
   }