virtio: console: Make read() return -ENODEV on hot-unplug

When a port is hot-unplugged while an app was blocked on a read() call,
the call was unblocked but would not get an error returned.

Return -ENODEV to ensure the app knows the port has gone away.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 47b710ca4ab3..e17ecf5d42b5 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -582,6 +582,9 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
                 if (ret < 0)
                         return ret;
         }
+        /* Port got hot-unplugged. */
+        if (!port->guest_connected)
+                return -ENODEV;
         /*
          * We could've received a disconnection message while we were
          * waiting for more data.