On Fri, Apr 26, 2013 at 04:34:02PM +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>
Why do this in virtio-pci and not in virtio.c?
If instead we correct the checks in virtio.c we
get less code, and all transports will benefit
automatically.
> ---
> hw/virtio/virtio-pci.c | 9 +++++++++
> hw/virtio/virtio.c | 18 ------------------
> 2 files changed, 9 insertions(+), 18 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index a1f15a8..7f6c7d1 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -400,6 +400,10 @@ static uint64_t virtio_pci_config_read(void *opaque,
> hwaddr addr,
> }
> addr -= config;
>
> + if (addr + size > proxy->vdev->config_len) {
> + return (uint32_t)-1;
> + }
> +
> switch (size) {
> case 1:
> val = virtio_config_readb(proxy->vdev, addr);
> @@ -430,6 +434,11 @@ static void virtio_pci_config_write(void *opaque, hwaddr
> addr,
> return;
> }
> addr -= config;
> +
> + if (addr + size > proxy->vdev->config_len) {
> + return;
> + }
> +
> /*
> * Virtio-PCI is odd. Ioports are LE but config space is target native
> * endian.
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 1c2282c..3397b5e 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -563,9 +563,6 @@ uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t
> addr)
>
> vdev->get_config(vdev, vdev->config);
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return (uint32_t)-1;
> -
> val = ldub_p(vdev->config + addr);
> return val;
> }
> @@ -576,9 +573,6 @@ uint32_t virtio_config_readw(VirtIODevice *vdev, uint32_t
> addr)
>
> vdev->get_config(vdev, vdev->config);
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return (uint32_t)-1;
> -
> val = lduw_p(vdev->config + addr);
> return val;
> }
> @@ -589,9 +583,6 @@ uint32_t virtio_config_readl(VirtIODevice *vdev, uint32_t
> addr)
>
> vdev->get_config(vdev, vdev->config);
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return (uint32_t)-1;
> -
> val = ldl_p(vdev->config + addr);
> return val;
> }
> @@ -600,9 +591,6 @@ void virtio_config_writeb(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> {
> uint8_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return;
> -
> stb_p(vdev->config + addr, val);
>
> if (vdev->set_config)
> @@ -613,9 +601,6 @@ void virtio_config_writew(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> {
> uint16_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return;
> -
> stw_p(vdev->config + addr, val);
>
> if (vdev->set_config)
> @@ -626,9 +611,6 @@ void virtio_config_writel(VirtIODevice *vdev, uint32_t
> addr, uint32_t data)
> {
> uint32_t val = data;
>
> - if (addr > (vdev->config_len - sizeof(val)))
> - return;
> -
> stl_p(vdev->config + addr, val);
>
> if (vdev->set_config)
> --
> 1.7.1
