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authorriastradh <riastradh@NetBSD.org>2022-03-28 12:37:26 +0000
committerriastradh <riastradh@NetBSD.org>2022-03-28 12:37:26 +0000
commitf0bfccf00b94619120a00a10bfbe375246c9d76f (patch)
treeb05ada95f6b9f204f72b118c7a8e87b32f7d9571 /sys/miscfs
parent357839325a75e6875bba371c52a5b199ec3277ed (diff)
specfs: Take an I/O reference across bdev/cdev_open.
- Revoke is used to invalidate all prior access control checks when device permissions are changing, so it must wait for .d_open to exit so any new access must go through new access control checks. - Revoke is used by vdevgone in xyz_detach to wait until all use of the driver's data structures have completed before xyz_detach frees them. So we need to make sure spec_close waits for .d_open too.
Diffstat (limited to 'sys/miscfs')
-rw-r--r--sys/miscfs/specfs/spec_vnops.c43
1 files changed, 34 insertions, 9 deletions
diff --git a/sys/miscfs/specfs/spec_vnops.c b/sys/miscfs/specfs/spec_vnops.c
index 6674cbdf3cf..109785a176b 100644
--- a/sys/miscfs/specfs/spec_vnops.c
+++ b/sys/miscfs/specfs/spec_vnops.c
@@ -1,4 +1,4 @@
-/* $NetBSD: spec_vnops.c,v 1.205 2022/03/28 12:37:18 riastradh Exp $ */
+/* $NetBSD: spec_vnops.c,v 1.206 2022/03/28 12:37:26 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 1.205 2022/03/28 12:37:18 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: spec_vnops.c,v 1.206 2022/03/28 12:37:26 riastradh Exp $");
#include <sys/param.h>
#include <sys/proc.h>
@@ -694,10 +694,10 @@ spec_open(void *v)
} */ *ap = v;
struct lwp *l = curlwp;
struct vnode *vp = ap->a_vp;
- dev_t dev;
+ dev_t dev, dev1;
int error;
enum kauth_device_req req;
- specnode_t *sn;
+ specnode_t *sn, *sn1;
specdev_t *sd;
spec_ioctl_t ioctl;
u_int gen = 0;
@@ -805,18 +805,34 @@ spec_open(void *v)
}
/*
- * Open the device. If .d_open returns ENXIO (device not
- * configured), the driver may not be loaded, so try
- * autoloading a module and then try .d_open again if anything
- * got loaded.
- *
* Because opening the device may block indefinitely, e.g. when
* opening a tty, and loading a module may cross into many
* other subsystems, we must not hold the vnode lock while
* calling .d_open, so release it now and reacquire it when
* done.
+ *
+ * Take an I/O reference so that any concurrent spec_close via
+ * spec_node_revoke will wait for us to finish calling .d_open.
+ * The vnode can't be dead at this point because we have it
+ * locked. Note that if revoked, the driver must interrupt
+ * .d_open before spec_close starts waiting for I/O to drain so
+ * this doesn't deadlock.
*/
VOP_UNLOCK(vp);
+ error = spec_io_enter(vp, &sn1, &dev1);
+ if (error) {
+ vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+ return error;
+ }
+ KASSERT(sn1 == sn);
+ KASSERT(dev1 == dev);
+
+ /*
+ * Open the device. If .d_open returns ENXIO (device not
+ * configured), the driver may not be loaded, so try
+ * autoloading a module and then try .d_open again if anything
+ * got loaded.
+ */
switch (vp->v_type) {
case VCHR:
do {
@@ -871,7 +887,16 @@ spec_open(void *v)
default:
__unreachable();
}
+
+ /*
+ * Release the I/O reference now that we have called .d_open,
+ * and reacquire the vnode lock. At this point, the device may
+ * have been revoked, so we must tread carefully. However, sn
+ * and sd remain valid pointers until we drop our reference.
+ */
+ spec_io_exit(vp, sn);
vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+ KASSERT(vp->v_specnode == sn);
/*
* If it has been revoked since we released the vnode lock and