On 07/19/2013 04:16 AM, Amit Shah wrote:
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
> ---
> drivers/char/virtio_console.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 6bf0df3..a39702a 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -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;
> +
What if the port is hot-unplugged after this check? Should we serialize
the hot plug with inbuf_lock here?
> 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;
> /*
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