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[Xen-changelog] [xen-unstable] [HVM] Disallow PTE updates and MMIO acces

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Subject: [Xen-changelog] [xen-unstable] [HVM] Disallow PTE updates and MMIO accesses from hypervisor mode
From: Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 16 Nov 2006 13:30:16 +0000
Delivery-date: Thu, 16 Nov 2006 05:30:04 -0800
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# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Node ID d0e9da9cc84a5c58c8b2a9591e02d74f50418d82
# Parent  2dea3be895138f1ac731ee2f241847e63831a1c5
[HVM] Disallow PTE updates and MMIO accesses from hypervisor mode
(prevents copy_to/from_guest from causing problems, for example).
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
 xen/arch/x86/mm/shadow/multi.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletion(-)

diff -r 2dea3be89513 -r d0e9da9cc84a xen/arch/x86/mm/shadow/multi.c
--- a/xen/arch/x86/mm/shadow/multi.c    Thu Nov 16 10:50:21 2006 +0000
+++ b/xen/arch/x86/mm/shadow/multi.c    Thu Nov 16 10:52:03 2006 +0000
@@ -2798,8 +2798,9 @@ static int sh_page_fault(struct vcpu *v,
      * We do not emulate user writes. Instead we use them as a hint that the
      * page is no longer a page table. This behaviour differs from native, but
      * it seems very unlikely that any OS grants user access to page tables.
+     * We also disallow guest PTE updates from within Xen.
-    if ( (regs->error_code & PFEC_user_mode) ||
+    if ( (regs->error_code & PFEC_user_mode) || !guest_mode(regs) ||
          x86_emulate_memop(&emul_ctxt, &shadow_emulator_ops) )
         SHADOW_PRINTK("emulator failure, unshadowing mfn %#lx\n", 
@@ -2839,6 +2840,8 @@ static int sh_page_fault(struct vcpu *v,
     goto done;
+    if ( !guest_mode(regs) )
+        goto not_a_shadow_fault;
     sh_audit_gw(v, &gw);
     unmap_walk(v, &gw);

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