[PATCH] dix: fix crash on XI 1.x grabs on disabled devices. (#54934)

[Peter Hutterer]

If the device is disabled, the sprite window is NULL and dereferencing
crashes the server.

This is only triggered for XI 1.x grabs (ProcXGrabDevice) as XI2 grabs would
trigger another code path, creating a sprite for the disabled device as if
detaching it (which is wrong and fixed with this patch too).

Grabbing a disabled device doesn't make sense as it won't send events
anyway. However, the protocol specs do not prohibit it, so we need to keep
it working.
Luckily, oldWin is only used for focus out events, which aren't necessary
given that the device is disabled.

X.Org Bug 54934 <http://bugs.freedesktop.org/show_bug.cgi?id=54934>

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 dix/events.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/dix/events.c b/dix/events.c
index d1931af..96778f7 100644
--- a/dix/events.c
+++ b/dix/events.c
@@ -1555,11 +1555,13 @@ ActivateKeyboardGrab(DeviceIntPtr keybd, GrabPtr grab, TimeStamp time,
     WindowPtr oldWin;
 
     /* slave devices need to float for the duration of the grab. */
-    if (grab->grabtype == XI2 &&
+    if (grab->grabtype == XI2 && keybd->enabled &&
         !(passive & ImplicitGrabMask) && !IsMaster(keybd))
         DetachFromMaster(keybd);
 
-    if (grabinfo->grab)
+    if (!keybd->enabled)
+        oldWin = NULL;
+    else if (grabinfo->grab)
         oldWin = grabinfo->grab->window;
     else if (keybd->focus)
         oldWin = keybd->focus->win;
@@ -1571,7 +1573,8 @@ ActivateKeyboardGrab(DeviceIntPtr keybd, GrabPtr grab, TimeStamp time,
         oldWin = keybd->focus->win;
     if (keybd->valuator)
         keybd->valuator->motionHintWindow = NullWindow;
-    DoFocusEvents(keybd, oldWin, grab->window, NotifyGrab);
+    if (oldWin)
+        DoFocusEvents(keybd, oldWin, grab->window, NotifyGrab);
     if (syncEvents.playingEvents)
         grabinfo->grabTime = syncEvents.time;
     else
-- 
1.7.11.2