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dix: avoid deferencing NULL PtrCtrl

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PtrCtrl really makes sense for relative pointing device only, absolute
devices such as touch devices do not have any PtrCtrl set.

In some cases, if the client issues a XGetPointerControl() immediatlely
after a ChangeMasterDeviceClasses() copied the touch device to the VCP,
a NULL pointer dereference will occur leading to a crash of Xwayland.

Check whether the PtrCtrl is not NULL in ProcGetPointerControl() and
return the default control values otherwise, to avoid the NULL pointer
dereference.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1519533
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
This commit is contained in:
Olivier Fourdan 2017-12-05 09:59:06 +01:00 committed by Adam Jackson
parent 60f4646ae1
commit 9f7a9be13d
1 changed files with 6 additions and 1 deletions
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7
dix/devices.c
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@ -2329,10 +2329,15 @@ int
ProcGetPointerControl(ClientPtr client)
{
DeviceIntPtr ptr = PickPointer(client);
PtrCtrl *ctrl = &ptr->ptrfeed->ctrl;
PtrCtrl *ctrl;
xGetPointerControlReply rep;
int rc;
if (ptr->ptrfeed)
ctrl = &ptr->ptrfeed->ctrl;
else
ctrl = &defaultPointerControl;
REQUEST_SIZE_MATCH(xReq);
rc = XaceHook(XACE_DEVICE_ACCESS, client, ptr, DixGetAttrAccess);