From: Markus Armbruster <armbru@redhat.com>
Date: Thu, 22 Nov 2007 09:10:13 +0100
Subject: [xen] fix behavior of invalid guest page mapping
Message-id: 873auy3dlm.fsf@pike.pond.sub.org
O-Subject: [PATCH RHEL-5.2] Fix behavior of invalid guest page mapping
Bugzilla: 254208

When dom0 attempts to map a guest page, and that request cannot be
satisfied, a page of zeroes is mapped instead.  This is wrong.  Access
to the invalid map should trap.

In Xen upstream, access triggers SIGBUS.

In RHEL-5.0, dom0 crashed hard (bug 249409).

linux-2.6-xen-fix-privcmd-to-remove-nopage-handler.patch hastily
resolved that bug for 5.1: dom0 no longer crashes.

This patch fixes the remaining issue: SIGBUS instead of mapping
zeroes.

It was tested by Chris Lalancette and myself.

Bug 254208: Xen: Mapping random guest pages returns the wrong
information

Please ACK.

Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Jon Masters <jcm@redhat.com>
Acked-by: Jarod Wilson <jwilson@redhat.com>

diff --git a/drivers/xen/privcmd/privcmd.c b/drivers/xen/privcmd/privcmd.c
index aab53ca..1aacaa2 100644
--- a/drivers/xen/privcmd/privcmd.c
+++ b/drivers/xen/privcmd/privcmd.c
@@ -217,8 +217,14 @@ static int privcmd_ioctl(struct inode *inode, struct file *file,
 }
 
 #ifndef HAVE_ARCH_PRIVCMD_MMAP
+unsigned long privcmd_nopfn(struct vm_area_struct *vma,
+				unsigned long address)
+{
+	return NOPFN_SIGBUS;
+}
+
 static struct vm_operations_struct privcmd_vm_ops = {
-	.nopage = NULL
+	.nopfn = privcmd_nopfn
 };
 
 static int privcmd_mmap(struct file * file, struct vm_area_struct * vma)