dri3: cap the version returned to the client

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@collabora.com>
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>

1 files changed, 13 insertions, 1 deletions

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);