Patchwork [resend] vmware_vga: Check cursor dimensions passed from guest to avoid buffer overflow

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Submitter Roland Dreier
Date Jan. 6, 2010, 4:43 a.m.
Message ID <adamy0rvo5l.fsf_-_@roland-alpha.cisco.com>
Download mbox | patch
Permalink /patch/42279/
State New
Headers show

Comments

Roland Dreier - Jan. 6, 2010, 4:43 a.m.
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>
---
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(-)
Anthony Liguori - Jan. 11, 2010, 4:01 p.m.
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 ++)
>
>
>
>

Patch

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 ++)