[Xen-changelog] [xen stable-4.5] x86: Disable the use of auto-translated PV guests

[patchbot@xxxxxxx]

commit 5fdf16f319ecd13f4a15d758fc914a8f07fbc357
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Thu Oct 12 16:01:42 2017 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 12 16:01:42 2017 +0200

    x86: Disable the use of auto-translated PV guests
    
    This is a minimal backport of c/s 92942fd3d469 "x86/mm: drop
    guest_{map,get_eff}_l1e() hooks" from Xen 4.7, which stated:
    
      Disallow the unmaintained and presumed broken translated-but-not-external
      paging mode combination ...
    
    It turns out that this mode is insecure to run with, as opposed to just 
simply
    broken.
    
    This is part of XSA-243.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/mm/paging.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/xen/arch/x86/mm/paging.c b/xen/arch/x86/mm/paging.c
index 37e2a12..8d7f5cb 100644
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -815,6 +815,15 @@ void paging_final_teardown(struct domain *d)
  * creation. */
 int paging_enable(struct domain *d, u32 mode)
 {
+    switch ( mode & (PG_external | PG_translate) )
+    {
+    case 0:
+    case PG_external | PG_translate:
+        break;
+    default:
+        return -EINVAL;
+    }
+
     if ( hap_enabled(d) )
         return hap_enable(d, mode | PG_HAP_enable);
     else
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.5

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