[src/trunk]: src/sys/miscfs/specfs Refuse to open a block device with zero op...

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

details:   https://anonhg.NetBSD.org/src/rev/c0b360144e3f
branches:  trunk
changeset: 824968:c0b360144e3f
user:      hannken <hannken%NetBSD.org@localhost>
date:      Sat Jun 24 12:14:21 2017 +0000

description:
Refuse to open a block device with zero open count when it has
a mountpoint set.  This may happen after forced detach or unplug
of a mounted block device.

diffstat:

 sys/miscfs/specfs/spec_vnops.c |  9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diffs (36 lines):

diff -r 5ccd08a36a29 -r c0b360144e3f sys/miscfs/specfs/spec_vnops.c
--- a/sys/miscfs/specfs/spec_vnops.c    Sat Jun 24 12:13:16 2017 +0000
+++ b/sys/miscfs/specfs/spec_vnops.c    Sat Jun 24 12:14:21 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: spec_vnops.c,v 1.173 2017/06/01 02:45:14 chs Exp $     */
+/*     $NetBSD: spec_vnops.c,v 1.174 2017/06/24 12:14:21 hannken Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.173 2017/06/01 02:45:14 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.174 2017/06/24 12:14:21 hannken Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -580,13 +580,16 @@
                 * For block devices, permit only one open.  The buffer
                 * cache cannot remain self-consistent with multiple
                 * vnodes holding a block device open.
+                *
+                * Treat zero opencnt with non-NULL mountpoint as open.
+                * This may happen after forced detach of a mounted device.
                 */
                mutex_enter(&device_lock);
                if (sn->sn_gone) {
                        mutex_exit(&device_lock);
                        return (EBADF);
                }
-               if (sd->sd_opencnt != 0) {
+               if (sd->sd_opencnt != 0 || sd->sd_mountpoint != NULL) {
                        mutex_exit(&device_lock);
                        return EBUSY;
                }