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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xie Yongji <xieyongji@bytedance.com>,
        Jason Wang <jasowang@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 171/292] virtio_console: Assure used length from device is limited
Date:   Mon, 19 Jul 2021 16:53:53 +0200
Message-Id: <20210719144948.129592440@linuxfoundation.org>
In-Reply-To: <20210719144942.514164272@linuxfoundation.org>
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From: Xie Yongji <xieyongji@bytedance.com>

[ Upstream commit d00d8da5869a2608e97cfede094dfc5e11462a46 ]

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@bytedance.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210525125622.1203-1-xieyongji@bytedance.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 1836cc56e357..673522874cec 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_t(size_t, len, buf->size);
 		buf->offset = 0;
 		port->stats.bytes_received += len;
 	}
@@ -1712,7 +1712,7 @@ 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_t(size_t, len, buf->size);
 		buf->offset = 0;
 
 		handle_control_message(vq->vdev, portdev, buf);
-- 
2.30.2