port-xen/49919: Bugs in xenevt.c

[liuw%liuw.name@localhost]

>Number:         49919
>Category:       port-xen
>Synopsis:       Bugs in xenevt.c
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    port-xen-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 22 10:10:07 +0000 2015
>Originator:     Wei Liu
>Release:        NetBSD HEAD
>Organization:
>Environment:
>Description:
There are several bugs in xenevt.c (userspace event channel driver).

1. The critical region is too small in xenevt_fread.
2. Range check under IOCTL_EVTCHN_UNBIND should be ">=".
3. Range check under IOCTL_EVTCHN_NOTIFY should be ">=".
>How-To-Repeat:

>Fix: