[PATCH] drm: Restrict ioctl size to kernel struct size

[Ville Syrjälä]

On Tue, Oct 22, 2013 at 10:38:03AM +0100, Chris Wilson wrote:
> Prevent the user from passing in an ioctl command with up to 16,383
> bytes specified for the struct to be allocated and copied, and
> instead only allocate enough space to satisfy the kernel.
> 
> Suggested-by: Pavel Roskin <proski at gnu.org>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Pavel Roskin <proski at gnu.org>
> Cc: dri-devel at lists.freedesktop.org

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/drm_drv.c | 30 +++++++++++++-----------------
>  1 file changed, 13 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 05ad9ba0a67e..8c5fbc9d41ad 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -354,6 +354,16 @@ static int drm_version(struct drm_device *dev, void *data,
>  	return err;
>  }
>  
> +static unsigned ioctl_size(unsigned kcmd, unsigned ucmd, unsigned *ksize, unsigned *usize)
> +{
> +	*ksize = _IOC_SIZE(kcmd);
> +	*usize = _IOC_SIZE(ucmd);
> +	if (*usize > *ksize)
> +		*usize = *ksize;
> +
> +	return kcmd;
> +}
> +
>  /**
>   * Called whenever a process performs an ioctl on /dev/drm.
>   *
> @@ -393,25 +403,11 @@ long drm_ioctl(struct file *filp,
>  		goto err_i1;
>  	if ((nr >= DRM_COMMAND_BASE) && (nr < DRM_COMMAND_END) &&
>  	    (nr < DRM_COMMAND_BASE + dev->driver->num_ioctls)) {
> -		u32 drv_size;
>  		ioctl = &dev->driver->ioctls[nr - DRM_COMMAND_BASE];
> -		drv_size = _IOC_SIZE(ioctl->cmd_drv);
> -		usize = asize = _IOC_SIZE(cmd);
> -		if (drv_size > asize)
> -			asize = drv_size;
> -		cmd = ioctl->cmd_drv;
> -	}
> -	else if ((nr >= DRM_COMMAND_END) || (nr < DRM_COMMAND_BASE)) {
> -		u32 drv_size;
> -
> +		cmd = ioctl_size(ioctl->cmd_drv, cmd, &asize, &usize);
> +	} else if ((nr >= DRM_COMMAND_END) || (nr < DRM_COMMAND_BASE)) {
>  		ioctl = &drm_ioctls[nr];
> -
> -		drv_size = _IOC_SIZE(ioctl->cmd);
> -		usize = asize = _IOC_SIZE(cmd);
> -		if (drv_size > asize)
> -			asize = drv_size;
> -
> -		cmd = ioctl->cmd;
> +		cmd = ioctl_size(ioctl->cmd, cmd, &asize, &usize);
>  	} else
>  		goto err_i1;
>  
> -- 
> 1.8.4.rc3
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Ville Syrjälä
Intel OTC