[PATCH xserver] dri3: cap the version returned to the client

[Emil Velikov]

On 13 March 2018 at 18:38, Emil Velikov <emil.l.velikov at gmail.com> wrote:
> From: Emil Velikov <emil.velikov at collabora.com>
>
> As per the protocol, the server should not return version greater than
> the one supported by the client.
>
> Add a spec quote and tweak the numbers accordingly.
>
> Fixes: 563138298868 ("dri3: Add DRI3 extension")
> Cc: Daniel Stone <daniels at collabora.com>
> Cc: Keith Packard <keithp at keithp.com>
> Signed-off-by: Emil Velikov <emil.velikov at collabora.com>
> ---
> Note: we might want this in the stable releases?
>
> Related: The DRI2 implementation has identical bug.
> Although fixing that (unlike DRI3) might cause some ill written apps to
> rightfully fall on their face.
>
> Should we bother - yay, nay are appreciated.
> ---
>  dri3/dri3_request.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/dri3/dri3_request.c b/dri3/dri3_request.c
> index 7f3f0d08c..fc258711b 100644
> --- a/dri3/dri3_request.c
> +++ b/dri3/dri3_request.c
> @@ -45,7 +45,19 @@ proc_dri3_query_version(ClientPtr client)
>      };
>
>      REQUEST_SIZE_MATCH(xDRI3QueryVersionReq);
> -    (void) stuff;
> +    /* From DRI3 proto:
> +     *
> +     * The client sends the highest supported version to the server
> +     * and the server sends the highest version it supports, but no
> +     * higher than the requested version.
> +     */
> +
> +    if (rep.majorVersion > stuff->majorVersion ||
> +        rep.minorVersion > stuff->minorVersion) {
> +        rep.majorVersion = stuff->majorVersion;
> +        rep.minorVersion = stuff->minorVersion;
> +    }
> +
>      if (client->swapped) {
>          swaps(&rep.sequenceNumber);
>          swapl(&rep.length);
> --
Humble ping anyone?

-Emil