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

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.

CC: <stable@vger.kernel.org>
Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Amit Shah 2013-07-29 14:23:21 +09:30 committed by Rusty Russell
parent 92d3453815
commit 96f97a8391
1 changed files with 5 additions and 1 deletions
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6
drivers/char/virtio_console.c
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@ -749,6 +749,10 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
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
@ -765,7 +769,7 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
if (ret < 0)
return ret;
}
/* Port got hot-unplugged. */
/* Port got hot-unplugged while we were waiting above. */
if (!port->guest_connected)
return -ENODEV;
/*