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virtio: console: return -ENODEV on all read operations after unplug 

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>
This commit is contained in:
Amit Shah 2013-07-29 14:23:21 +09:30 committed by Greg Kroah-Hartman
parent 183c6a6b4e
commit a57425e942
1 changed files with 5 additions and 1 deletions
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6
drivers/char/virtio_console.c
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@ -633,6 +633,10 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
port = filp->private_data; port = filp->private_data;
/* Port is hot-unplugged. */
if (!port->guest_connected)
return -ENODEV;
if (!port_has_data(port)) { if (!port_has_data(port)) {
/* /*
* If nothing's connected on the host just return 0 in * If nothing's connected on the host just return 0 in
@ -649,7 +653,7 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
if (ret < 0) if (ret < 0)
return ret; return ret;
} }
/* Port got hot-unplugged. */ /* Port got hot-unplugged while we were waiting above. */
if (!port->guest_connected) if (!port->guest_connected)
return -ENODEV; return -ENODEV;
/* /*