[Pkg-xen-changes] [xen] 40/48: x86: don't allow page table updates on non-PV page tables in do_mmu_update()

[Ian James Campbell]

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ijc pushed a commit to branch feature/patch-names
in repository xen.

commit 8b654139e555941160766a77999f04a9b09c149e
Author: Jan Beulich <jbeulich at suse.com>
Date:   Tue Nov 18 14:27:46 2014 +0100

    x86: don't allow page table updates on non-PV page tables in do_mmu_update()
    
    paging_write_guest_entry() and paging_cmpxchg_guest_entry() aren't
    consistently supported for non-PV guests (they'd deref NULL for PVH or
    non-HAP HVM ones). Don't allow respective MMU_* operations on the
    page tables of such domains.
    
    This is CVE-2014-8594 / XSA-109.
    
    Signed-off-by: Jan Beulich <jbeulich at suse.com>
    Acked-by: Tim Deegan <tim at xen.org>
    master commit: e4292c5aac41b80f33d4877104348d5ee7c95aa4
    master date: 2014-11-18 14:15:21 +0100
    
    Patch-Name: xsa109.diff
---
 xen/arch/x86/mm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index fdc5ed3..f88323f 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3508,6 +3508,10 @@ long do_mmu_update(
         {
             p2m_type_t p2mt;
 
+            rc = -EOPNOTSUPP;
+            if ( unlikely(paging_mode_refcounts(pt_owner)) )
+                break;
+
             xsm_needed |= XSM_MMU_NORMAL_UPDATE;
             if ( get_pte_flags(req.val) & _PAGE_PRESENT )
             {

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