[src/trunk]: src/sys/miscfs/specfs specfs: sn_gone cannot be set while we hol...

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

details:   https://anonhg.NetBSD.org/src/rev/c0cd4362062a
branches:  trunk
changeset: 364505:c0cd4362062a
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Mon Mar 28 12:35:44 2022 +0000

description:
specfs: sn_gone cannot be set while we hold the vnode lock.

Revoke runs with the vnode lock too, which is exclusive.  Add an
assertion to this effect in spec_node_revoke to make it clear.

diffstat:

 sys/miscfs/specfs/spec_vnops.c |  23 ++++++++---------------
 1 files changed, 8 insertions(+), 15 deletions(-)

diffs (65 lines):

diff -r 60c601c53d5c -r c0cd4362062a sys/miscfs/specfs/spec_vnops.c
--- a/sys/miscfs/specfs/spec_vnops.c    Mon Mar 28 12:35:35 2022 +0000
+++ b/sys/miscfs/specfs/spec_vnops.c    Mon Mar 28 12:35:44 2022 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: spec_vnops.c,v 1.194 2022/03/28 12:35:35 riastradh Exp $       */
+/*     $NetBSD: spec_vnops.c,v 1.195 2022/03/28 12:35:44 riastradh Exp $       */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.194 2022/03/28 12:35:35 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.195 2022/03/28 12:35:44 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/proc.h>
@@ -402,6 +402,8 @@
        specnode_t *sn;
        specdev_t *sd;
 
+       KASSERT(VOP_ISLOCKED(vp) == LK_EXCLUSIVE);
+
        sn = vp->v_specnode;
        sd = sn->sn_dev;
 
@@ -552,11 +554,8 @@
 
        /*
         * Acquire an open reference -- as long as we hold onto it, and
-        * the vnode isn't revoked, it can't be closed.
-        *
-        * But first check whether it has been revoked -- if so, we
-        * can't acquire more open references and we must fail
-        * immediately with EBADF.
+        * the vnode isn't revoked, it can't be closed, and the vnode
+        * can't be revoked until we release the vnode lock.
         */
        mutex_enter(&device_lock);
        switch (vp->v_type) {
@@ -565,10 +564,7 @@
                 * Character devices can accept opens from multiple
                 * vnodes.
                 */
-               if (sn->sn_gone) {
-                       error = EBADF;
-                       break;
-               }
+               KASSERT(!sn->sn_gone);
                sd->sd_opencnt++;
                sn->sn_opencnt++;
                break;
@@ -581,10 +577,7 @@
                 * Treat zero opencnt with non-NULL mountpoint as open.
                 * This may happen after forced detach of a mounted device.
                 */
-               if (sn->sn_gone) {
-                       error = EBADF;
-                       break;
-               }
+               KASSERT(!sn->sn_gone);
                if (sd->sd_opencnt != 0 || sd->sd_mountpoint != NULL) {
                        error = EBUSY;
                        break;