linux-kernel - [PATCH] virtio_console: Assure used length from device is limited

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Message-Id: <20210525045304.1085-1-xieyongji@bytedance.com>
Date:   Tue, 25 May 2021 12:53:04 +0800
From:   Xie Yongji <xieyongji@...edance.com>
To:     amit@...nel.org, mst@...hat.com, jasowang@...hat.com
Cc:     virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] virtio_console: Assure used length from device is limited

The buf->len might come from an untrusted device. This
ensures the value would not exceed the size of the buffer
to avoid data corruption or loss.

Signed-off-by: Xie Yongji <xieyongji@...edance.com>
---
 drivers/char/virtio_console.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 1c40ca6d76ba..598863e6daf8 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -475,7 +475,7 @@ static struct port_buffer *get_inbuf(struct port *port)
 
 	buf = virtqueue_get_buf(port->in_vq, &len);
 	if (buf) {
-		buf->len = len;
+		buf->len = min(len, buf->size);
 		buf->offset = 0;
 		port->stats.bytes_received += len;
 	}
@@ -1709,7 +1709,7 @@ static void control_work_handler(struct work_struct *work)
 	while ((buf = virtqueue_get_buf(vq, &len))) {
 		spin_unlock(&portdev->c_ivq_lock);
 
-		buf->len = len;
+		buf->len = min(len, buf->size);
 		buf->offset = 0;
 
 		handle_control_message(vq->vdev, portdev, buf);
-- 
2.11.0