[src/trunk]: src/sys/kern NULL-check the structure pointer, not the address o...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/33b3f1890fb7
branches:  trunk
changeset: 846420:33b3f1890fb7
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sat Nov 16 10:07:53 2019 +0000

description:
NULL-check the structure pointer, not the address of its first field. Also
add KASSERT. For clarity, and to appease kUBSan.

diffstat:

 sys/kern/vfs_mount.c |  9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diffs (33 lines):

diff -r 45ac2c3f6485 -r 33b3f1890fb7 sys/kern/vfs_mount.c
--- a/sys/kern/vfs_mount.c      Sat Nov 16 10:05:44 2019 +0000
+++ b/sys/kern/vfs_mount.c      Sat Nov 16 10:07:53 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: vfs_mount.c,v 1.71 2019/08/19 09:32:42 christos Exp $  */
+/*     $NetBSD: vfs_mount.c,v 1.72 2019/11/16 10:07:53 maxv Exp $      */
 
 /*-
  * Copyright (c) 1997-2011 The NetBSD Foundation, Inc.
@@ -67,7 +67,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.71 2019/08/19 09:32:42 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: vfs_mount.c,v 1.72 2019/11/16 10:07:53 maxv Exp $");
 
 #include <sys/param.h>
 #include <sys/kernel.h>
@@ -420,11 +420,12 @@
                TAILQ_REMOVE(&mp->mnt_vnodelist, mvip, vi_mntvnodes);
                VIMPL_TO_VNODE(mvip)->v_usecount = 0;
 again:
-               vp = VIMPL_TO_VNODE(vip);
-               if (vp == NULL) {
+               if (vip == NULL) {
                        mutex_exit(&mntvnode_lock);
                        return NULL;
                }
+               vp = VIMPL_TO_VNODE(vip);
+               KASSERT(vp != NULL);
                mutex_enter(vp->v_interlock);
                if (vnis_marker(vp) ||
                    vdead_check(vp, (do_wait ? 0 : VDEAD_NOWAIT)) ||