linux-kernel - [PATCH V3 02/10] virtio_console: validate max_nr

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Date:   Tue, 19 Oct 2021 15:01:44 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     mst@...hat.com, jasowang@...hat.com
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, f.hetzelt@...berlin.de,
        david.kaplan@....com, konrad.wilk@...cle.com,
        Amit Shah <amit@...nel.org>
Subject: [PATCH V3 02/10] 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@...nel.org>
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/char/virtio_console.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 7eaf303a7a86..660c5c388c29 100644
--- 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;
 	}
 
-- 
2.25.1