Re: [BUG] Intel xorg driver 2.20.2 overlay off-by-one bug

On Sun, 12 Aug 2012 10:01:44 +0100, Russell King - ARM Linux linux@arm.linux.org.uk wrote:

While reading through the Intel driver code, I spotted this in I830SetPortAttributeOverlay:

    } else if (attribute == xvPipe) {
            xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(scrn);
            if ((value < -1) || (value > xf86_config->num_crtc))
                    return BadValue;
            if (value < 0)
                    adaptor_priv->desired_crtc = NULL;
            else
                    adaptor_priv->desired_crtc = xf86_config->crtc[value];

This allows value == xf86_config->num_crtc to be valid, which would be the CRTC number _after_ the last one in the array. Presumably this is not desired, and the test should be ">=".

Thanks for bringing this to our attention and poking Dave, who promptly pushed a patch to fix the bug. -Chris