On 07/19/2013 04:16 AM, Amit Shah wrote:
> Between poll() being called and processed, the port can be unplugged.
> Check if this happened, and bail out.
>
> Signed-off-by: Amit Shah <amit.shah@xxxxxxxxxx>
> ---
> drivers/char/virtio_console.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7728af9..1d4b748 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -967,6 +967,10 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
> unsigned int ret;
>
> port = filp->private_data;
> + if (!port->guest_connected) {
> + /* Port was unplugged before we could proceed */
> + return POLLHUP;
> + }
> poll_wait(filp, &port->waitqueue, wait);
>
> if (!port->guest_connected) {
Looks still racy here. Unlike port_fops_read() which check
will_read_block(). If unplug happens after the check but before the
poll_wait(), caller will be blocked forever.
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