Messages in this thread Patch in this message |  | | From | Alexander Shishkin <> | | Subject | [PATCH v1 2/6] virtio console: Harden port adding | | Date | Thu, 19 Jan 2023 15:57:17 +0200 |
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From: Andi Kleen <ak@linux.intel.com>
The ADD_PORT operation reads and sanity checks the port id multiple times from the untrusted host. This is not safe because a malicious host could change it between reads.
Read the port id only once and cache it for subsequent uses.
Signed-off-by: Andi Kleen <ak@linux.intel.com> Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Amit Shah <amit@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/char/virtio_console.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c index f4fd5fe7cd3a..6599c2956ba4 100644 --- a/drivers/char/virtio_console.c +++ b/drivers/char/virtio_console.c @@ -1563,10 +1563,13 @@ static void handle_control_message(struct virtio_device *vdev, struct port *port; size_t name_size; int err; + unsigned id; cpkt = (struct virtio_console_control *)(buf->buf + buf->offset); - port = find_port_by_id(portdev, virtio32_to_cpu(vdev, cpkt->id)); + /* Make sure the host cannot change id under us */ + id = virtio32_to_cpu(vdev, READ_ONCE(cpkt->id)); + port = find_port_by_id(portdev, id); if (!port && cpkt->event != cpu_to_virtio16(vdev, VIRTIO_CONSOLE_PORT_ADD)) { /* No valid header at start of buffer. Drop it. */ @@ -1583,15 +1586,14 @@ static void handle_control_message(struct virtio_device *vdev, send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1); break; } - if (virtio32_to_cpu(vdev, cpkt->id) >= - portdev->max_nr_ports) { + if (id >= portdev->max_nr_ports) { dev_warn(&portdev->vdev->dev, "Request for adding port with " "out-of-bound id %u, max. supported id: %u\n", cpkt->id, portdev->max_nr_ports - 1); break; } - add_port(portdev, virtio32_to_cpu(vdev, cpkt->id)); + add_port(portdev, id); break; case VIRTIO_CONSOLE_PORT_REMOVE: unplug_port(port); -- 2.39.0
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