virtio_console: validate max_nr_ports before trying to use it

We calculate nr_ports based on the max_nr_ports:

nr_queues = use_multiport(portdev) ? (nr_ports + 1) * 2 : 2;

If the device advertises a large max_nr_ports, we will end up with a
integer overflow. Fixing this by validating the max_nr_ports and fail
the probe for invalid max_nr_ports in this case.

Cc: Amit Shah <amit@kernel.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20211019070152.8236-3-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 7eaf303a7a86f9230ad3b2d906eaacbf211589a3..660c5c388c291759838e686c387f370005690719 100644 (file)
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -28,6 +28,7 @@
 #include "../tty/hvc/hvc_console.h"
 
 #define is_rproc_enabled IS_ENABLED(CONFIG_REMOTEPROC)
+#define VIRTCONS_MAX_PORTS 0x8000
 
 /*
  * This is a global struct for storing common data for all the devices
@@ -2036,6 +2037,14 @@ static int virtcons_probe(struct virtio_device *vdev)
            virtio_cread_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT,
                                 struct virtio_console_config, max_nr_ports,
                                 &portdev->max_nr_ports) == 0) {
+               if (portdev->max_nr_ports == 0 ||
+                   portdev->max_nr_ports > VIRTCONS_MAX_PORTS) {
+                       dev_err(&vdev->dev,
+                               "Invalidate max_nr_ports %d",
+                               portdev->max_nr_ports);
+                       err = -EINVAL;
+                       goto free;
+               }
                multiport = true;
        }