check for null vioblk info

If {c,m}alloc fail, info could be NULL and result in NULL deref.

Reported by Ilja van Sprundel.

ok mlarkin@

diff --git a/usr.sbin/vmd/virtio.c b/usr.sbin/vmd/virtio.c
index 30580c0..8150047 100644 (file)
--- a/usr.sbin/vmd/virtio.c
+++ b/usr.sbin/vmd/virtio.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: virtio.c,v 1.94 2021/08/29 11:14:27 dv Exp $  */
+/*     $OpenBSD: virtio.c,v 1.95 2021/08/29 11:41:27 dv Exp $  */
 
 /*
  * Copyright (c) 2015 Mike Larkin <mlarkin@openbsd.org>
@@ -521,6 +521,11 @@ vioblk_notifyq(struct vioblk_dev *dev)
                                info = vioblk_start_read(dev,
                                    cmd.sector + secbias, secdata_desc->len);
 
+                               if (info == NULL) {
+                                       log_warnx("vioblk: can't start read");
+                                       goto out;
+                               }
+
                                /* read the data, use current data descriptor */
                                secdata = vioblk_finish_read(info);
                                if (secdata == NULL) {