From 6b880aa521fb191dfd0f33e8f416099b2a4656a5 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Wed, 15 Oct 2014 13:16:51 +0000
Subject: [PATCH] When vnode bypass cannot be performed on the cdev file
 descriptor for read/write/poll/ioctl, call standard vnode filedescriptor fop.
  This restores the special handling for terminals by calling the deadfs VOP,
 instead of always returning ENXIO for destroyed devices or revoked terminals.

Since destroyed (and not revoked) device would use devfs_specops VOP
vector, make dead_read/write/poll non-static and fill VOP table with
pointers to the functions, to instead of VOP_PANIC.

Noted and reviewed by:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
---
 sys/fs/deadfs/dead_vnops.c |  9 +++------
 sys/fs/devfs/devfs_vnops.c | 23 ++++++++++++++++-------
 sys/sys/vnode.h            |  3 +++
 3 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/sys/fs/deadfs/dead_vnops.c b/sys/fs/deadfs/dead_vnops.c
index 8c0ebcbbdadc..35eded0884e0 100644
--- a/sys/fs/deadfs/dead_vnops.c
+++ b/sys/fs/deadfs/dead_vnops.c
@@ -43,9 +43,6 @@
  */
 static vop_lookup_t	dead_lookup;
 static vop_open_t	dead_open;
-static vop_poll_t	dead_poll;
-static vop_read_t	dead_read;
-static vop_write_t	dead_write;
 static vop_getwritemount_t dead_getwritemount;
 static vop_rename_t	dead_rename;
 
@@ -130,7 +127,7 @@ dead_open(ap)
  * Vnode op for read
  */
 /* ARGSUSED */
-static int
+int
 dead_read(ap)
 	struct vop_read_args /* {
 		struct vnode *a_vp;
@@ -151,7 +148,7 @@ dead_read(ap)
  * Vnode op for write
  */
 /* ARGSUSED */
-static int
+int
 dead_write(ap)
 	struct vop_write_args /* {
 		struct vnode *a_vp;
@@ -163,7 +160,7 @@ dead_write(ap)
 	return (EIO);
 }
 
-static int
+int
 dead_poll(ap)
 	struct vop_poll_args *ap;
 {
diff --git a/sys/fs/devfs/devfs_vnops.c b/sys/fs/devfs/devfs_vnops.c
index d7009a49dd45..07b18037b8ea 100644
--- a/sys/fs/devfs/devfs_vnops.c
+++ b/sys/fs/devfs/devfs_vnops.c
@@ -737,8 +737,10 @@ devfs_ioctl_f(struct file *fp, u_long com, void *data, struct ucred *cred, struc
 
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
-	if (error)
+	if (error != 0) {
+		error = vnops.fo_ioctl(fp, com, data, cred, td);
 		return (error);
+	}
 
 	if (com == FIODTYPE) {
 		*(int *)data = dsw->d_flags & D_TYPEMASK;
@@ -1152,8 +1154,10 @@ devfs_poll_f(struct file *fp, int events, struct ucred *cred, struct thread *td)
 
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
-	if (error)
-		return (poll_no_poll(events));
+	if (error != 0) {
+		error = vnops.fo_poll(fp, events, cred, td);
+		return (error);
+	}
 	error = dsw->d_poll(dev, events, td);
 	td->td_fpop = fpop;
 	dev_relthread(dev, ref);
@@ -1185,8 +1189,10 @@ devfs_read_f(struct file *fp, struct uio *uio, struct ucred *cred,
 		return (EINVAL);
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
-	if (error)
+	if (error != 0) {
+		error = vnops.fo_read(fp, uio, cred, flags, td);
 		return (error);
+	}
 	resid = uio->uio_resid;
 	ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT);
 	if (ioflag & O_DIRECT)
@@ -1660,8 +1666,10 @@ devfs_write_f(struct file *fp, struct uio *uio, struct ucred *cred,
 		return (EINVAL);
 	fpop = td->td_fpop;
 	error = devfs_fp_check(fp, &dev, &dsw, &ref);
-	if (error)
+	if (error != 0) {
+		error = vnops.fo_write(fp, uio, cred, flags, td);
 		return (error);
+	}
 	KASSERT(uio->uio_td == td, ("uio_td %p is not td %p", uio->uio_td, td));
 	ioflag = fp->f_flag & (O_NONBLOCK | O_DIRECT | O_FSYNC);
 	if (ioflag & O_DIRECT)
@@ -1744,8 +1752,9 @@ static struct vop_vector devfs_specops = {
 	.vop_mknod =		VOP_PANIC,
 	.vop_open =		devfs_open,
 	.vop_pathconf =		devfs_pathconf,
+	.vop_poll =		dead_poll,
 	.vop_print =		devfs_print,
-	.vop_read =		VOP_PANIC,
+	.vop_read =		dead_read,
 	.vop_readdir =		VOP_PANIC,
 	.vop_readlink =		VOP_PANIC,
 	.vop_reallocblks =	VOP_PANIC,
@@ -1761,7 +1770,7 @@ static struct vop_vector devfs_specops = {
 	.vop_strategy =		VOP_PANIC,
 	.vop_symlink =		VOP_PANIC,
 	.vop_vptocnp =		devfs_vptocnp,
-	.vop_write =		VOP_PANIC,
+	.vop_write =		dead_write,
 };
 
 /*
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index 8610aca03de3..c78b9d18f7a2 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -758,6 +758,9 @@ int	vop_enoent(struct vop_generic_args *ap);
 int	vop_enotty(struct vop_generic_args *ap);
 int	vop_null(struct vop_generic_args *ap);
 int	vop_panic(struct vop_generic_args *ap);
+int	dead_poll(struct vop_poll_args *ap);
+int	dead_read(struct vop_read_args *ap);
+int	dead_write(struct vop_write_args *ap);
 
 /* These are called from within the actual VOPS. */
 void	vop_create_post(void *a, int rc);