[Xen-devel] [PATCH 04/11] nEPT: Do further permission check for sucessful translation.

[xiantao.zhang@xxxxxxxxx]

From: Zhang Xiantao <xiantao.zhang@xxxxxxxxx>

If permission check fails, inject EPT violation vmexit to guest. 

Signed-off-by: Zhang Xiantao <xiantao.zhang@xxxxxxxxx>
Signed-off-by: Xu Dongxiao<dongxiao.xu@xxxxxxxxx>
---
 xen/arch/x86/mm/hap/nested_ept.c |   24 ++++++++++++++++++++----
 1 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/mm/hap/nested_ept.c b/xen/arch/x86/mm/hap/nested_ept.c
index da868e7..2d733a8 100644
--- a/xen/arch/x86/mm/hap/nested_ept.c
+++ b/xen/arch/x86/mm/hap/nested_ept.c
@@ -272,6 +272,16 @@ unmap:
     return ret;
 }
 
+static
+bool_t nept_permission_check(uint32_t rwx_acc, uint32_t rwx_bits)
+{
+    if ( ((rwx_acc & 0x1) && !(rwx_bits & 0x1)) ||
+        ((rwx_acc & 0x2) && !(rwx_bits & 0x2 )) ||
+        ((rwx_acc & 0x4) && !(rwx_bits & 0x4 )) )
+        return 0;
+    return 1;
+}
+
 /* Translate a L2 guest address to L1 gpa via L1 EPT paging structure */
 
 int nept_translate_l2ga(struct vcpu *v, paddr_t l2ga, 
@@ -301,11 +311,17 @@ int nept_translate_l2ga(struct vcpu *v, paddr_t l2ga,
                 rwx_bits = gw.l4e.l4 & gw.l3e.l3  & 0x7;
                 *page_order = 18;
             }
-            else
+            else {
                 gdprintk(XENLOG_ERR, "Uncorrect l1 entry!\n");
-
-            *l1gfn = guest_l1e_get_paddr(gw.l1e) >> PAGE_SHIFT;
-            break;
+                BUG();
+            }
+            if ( nept_permission_check(rwx_acc, rwx_bits) )
+            {
+                 *l1gfn = guest_l1e_get_paddr(gw.l1e) >> PAGE_SHIFT;
+                 break;
+            }
+            rc = EPT_TRANSLATE_VIOLATION;
+        /* Fall through to EPT violation if permission check fails. */
         case EPT_TRANSLATE_VIOLATION:
             *exit_qual = (*exit_qual & 0xffffffc0) | (rwx_bits << 3) | rwx_acc;
             *exit_reason = EXIT_REASON_EPT_VIOLATION;
-- 
1.7.1


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