On Tue, May 07, 2013 at 01:42:49PM +0800, Jason Wang wrote:
> There are several several issues in the current checking:
>
> - The check was based on the minus of unsigned values which can overflow
> - It was done after .{set|get}_config() which can lead crash when config_len
> is zero since vdev->config is NULL
>
> Fix this by:
>
> - Validate the address in virtio_pci_config_{read|write}() before
> .{set|get}_config
> - Use addition instead minus to do the validation
>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Cc: Petr Matousek <pmato...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
Acked-by: Michael S. Tsirkin <m...@redhat.com>
> ---
> Changes from V1:
> - Doing check in virtio.c instead of virtio-pci.c
> - Drop the patch of virtio-ccw and s390-virtio-bus
> ---
> hw/virtio/virtio.c | 30 ++++++++++++++++++------------
> 1 files changed, 18 insertions(+), 12 deletions(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 53a0d90..8176c14 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -568,10 +568,11 @@ uint32_t virtio_config_readb(VirtIODevice *vdev,
> uint32_t addr)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint8_t val;
>
> - k->get_config(vdev, vdev->config);
> -
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return (uint32_t)-1;
> + }
> +
> + k->get_config(vdev, vdev->config);
>
> val = ldub_p(vdev->config + addr);
> return val;
> @@ -582,10 +583,11 @@ uint32_t virtio_config_readw(VirtIODevice *vdev,
> uint32_t addr)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint16_t val;
>
> - k->get_config(vdev, vdev->config);
> -
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return (uint32_t)-1;
> + }
> +
> + k->get_config(vdev, vdev->config);
>
> val = lduw_p(vdev->config + addr);
> return val;
> @@ -596,10 +598,11 @@ uint32_t virtio_config_readl(VirtIODevice *vdev,
> uint32_t addr)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint32_t val;
>
> - k->get_config(vdev, vdev->config);
> -
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return (uint32_t)-1;
> + }
> +
> + k->get_config(vdev, vdev->config);
>
> val = ldl_p(vdev->config + addr);
> return val;
> @@ -610,8 +613,9 @@ void virtio_config_writeb(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint8_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return;
> + }
>
> stb_p(vdev->config + addr, val);
>
> @@ -625,8 +629,9 @@ void virtio_config_writew(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint16_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return;
> + }
>
> stw_p(vdev->config + addr, val);
>
> @@ -640,8 +645,9 @@ void virtio_config_writel(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> uint32_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> + if (addr + sizeof(val) > vdev->config_len) {
> return;
> + }
>
> stl_p(vdev->config + addr, val);
>
> --
> 1.7.1
