[PATCH] drm/vmwgfx: integer underflow in vmw_cmd_dx_set_shader() leading to an invalid read

[Thomas Hellstrom]

Thanks, Murray,

I'll include in the next vmwgfx-fixes pull request.

On Mon, 2019-05-20 at 21:57 +1200, Murray McAllister wrote:
> If SVGA_3D_CMD_DX_SET_SHADER is called with a shader ID
> of SVGA3D_INVALID_ID, and a shader type of
> SVGA3D_SHADERTYPE_INVALID, the calculated binding.shader_slot
> will be 4294967295, leading to an out-of-bounds read in
> vmw_binding_loc()
> when the offset is calculated.
> 
> Signed-off-by: Murray McAllister <murray.mcallister at gmail.com>
> ---
>  drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
> b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
> index 2ff7ba04d8c8..9aeb5448cfc1 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c
> @@ -2193,7 +2193,8 @@ static int vmw_cmd_dx_set_shader(struct
> vmw_private *dev_priv,
>  
>  	cmd = container_of(header, typeof(*cmd), header);
>  
> -	if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX) {
> +	if (cmd->body.type >= SVGA3D_SHADERTYPE_DX10_MAX ||
> +	    cmd->body.type < SVGA3D_SHADERTYPE_MIN) {
>  		VMW_DEBUG_USER("Illegal shader type %u.\n",
>  			       (unsigned int) cmd->body.type);
>  		return -EINVAL;