[PATCH 1/2] dix: Return BadWindow rather than BadMatch from dixLookupWindow

Christopher James Halse Rogers christopher.halse.rogers at canonical.com
Wed Jan 4 17:22:39 PST 2012

dixLookupWindow uses dixLookupDrawable internally, which returns
BadMatch when the XID matches a non-Window drawable.  Users
of dixLookupWindow don't care about this, just that it's not
a valid Window.

This is a generalised version of the fix for X.Org Bug 23562,
where GetProperty was incorrectly returning BadMatch. Auditing other
window requests, all that I checked would incorrectly return BadMatch
in these circumstances.  An incomplete list of calls that could
incorrectly return BadMatch is: ListProperties, SetSelectionOwner,

None of the callers of dixLookupWindow, except for GetProperty, check
for BadMatch

Signed-off-by: Christopher James Halse Rogers <christopher.halse.rogers at canonical.com>
 dix/dixutils.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/dix/dixutils.c b/dix/dixutils.c
index 00bbde6..9ff91be 100644
--- a/dix/dixutils.c
+++ b/dix/dixutils.c
@@ -225,7 +225,15 @@ dixLookupWindow(WindowPtr *pWin, XID id, ClientPtr client, Mask access)
     int rc;
     rc = dixLookupDrawable((DrawablePtr*)pWin, id, client, M_WINDOW, access);
-    return (rc == BadDrawable) ? BadWindow : rc;
+    /* dixLookupDrawable returns BadMatch iff id is a valid Drawable
+       but is not a Window. Users of dixLookupWindow expect a BadWindow
+       error in this case; they don't care that it's a valid non-Window XID */
+    if (rc == BadMatch)
+	rc = BadWindow;
+    /* Similarly, users of dixLookupWindow don't want BadDrawable. */
+    if (rc == BadDrawable)
+	rc = BadWindow;
+    return rc;

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