[ 06/12] virtio: console: return -ENODEV on all read operations after unplug

Greg Kroah-Hartman
2013-08-13T06:41:13Z

From: Amit Shah <amit.shah@redhat.com>

commit 96f97a83910cdb9d89d127c5ee523f8fc040a804 upstream.

If a port gets unplugged while a user is blocked on read(), -ENODEV is
returned. However, subsequent read()s returned 0, indicating there's no
host-side connection (but not indicating the device went away).

This also happened when a port was unplugged and the user didn't have
any blocking operation pending. If the user didn't monitor the SIGIO
signal, they won't have a chance to find out if the port went away.

Fix by returning -ENODEV on all read()s after the port gets unplugged.
write() already behaves this way.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/char/virtio_console.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -625,6 +625,10 @@ static ssize_t port_fops_read(struct fil

port = filp->private_data;

+ /* Port is hot-unplugged. */
+ if (!port->guest_connected)
+ return -ENODEV;
+
if (!port_has_data(port)) {
/*
* If nothing's connected on the host just return 0 in
@@ -641,7 +645,7 @@ static ssize_t port_fops_read(struct fil
if (ret < 0)
return ret;
}
- /* Port got hot-unplugged. */
+ /* Port got hot-unplugged while we were waiting above. */
if (!port->guest_connected)
return -ENODEV;
/*