Re: [Qemu-devel] [PATCH resend] vmware_vga: Check cursor dimensions passed from guest to avoid buffer overflow

[Anthony Liguori <anthony@codemonkey.ws>]

On 01/05/2010 10:43 PM, Roland Dreier wrote:
> Check that the cursor dimensions passed from the guest for the
> DEFINE_CURSOR command don't overflow the available space in the
> cursor.image[] or cursor.mask[] arrays before copying data from the
> guest into those arrays.
>
> Signed-off-by: Roland Dreier<rolandd@cisco.com>
>    

Applied.  Thanks.

Regards,

Anthony Liguori
> ---
> Hi Anthony,
>
> as far as I can tell this seems to have slipped through the cracks.  I
> think this is fairly important: it is a guest-triggerable stack smashing
> attack in the worst case.
>
> Thanks,
>    Roland
>
>   hw/vmware_vga.c |    7 +++++++
>   1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/hw/vmware_vga.c b/hw/vmware_vga.c
> index 7ab1c79..5e969ae 100644
> --- a/hw/vmware_vga.c
> +++ b/hw/vmware_vga.c
> @@ -562,6 +562,13 @@ static void vmsvga_fifo_run(struct vmsvga_state_s *s)
>               cursor.height = y = vmsvga_fifo_read(s);
>               vmsvga_fifo_read(s);
>               cursor.bpp = vmsvga_fifo_read(s);
> +
> +	    if (SVGA_BITMAP_SIZE(x, y)>  sizeof cursor.mask ||
> +		SVGA_PIXMAP_SIZE(x, y, cursor.bpp)>  sizeof cursor.image) {
> +		    args = SVGA_BITMAP_SIZE(x, y) + SVGA_PIXMAP_SIZE(x, y, cursor.bpp);
> +		    goto badcmd;
> +	    }
> +
>               for (args = 0; args<  SVGA_BITMAP_SIZE(x, y); args ++)
>                   cursor.mask[args] = vmsvga_fifo_read_raw(s);
>               for (args = 0; args<  SVGA_PIXMAP_SIZE(x, y, cursor.bpp); args ++)
>
>
>
>